So, to me, an ideal turn-based RPG would require the player to put genuine thought into how they go about battling; simply spamming the Attack command or a powerful spell and healing when necessary wouldn't be enough to win the day.
Most RPGs I've played, however, fall into this trapping: hit the enemy really hard and heal when your HP gets low until you eventually whittle your opponent's HP down. This doesn't make those games inherently bad, but I think it stops them from being as fun as they could be.
...which leads me into my main question: how does one go about encouraging strategy and tactical decision-making in turn-based combat?
Yep, this is all too common. Devs who don't think their combat through. That don't realize it's a feature and should be fleshed out as one. A "power fantasy" is worthless if the player doesn't feel powerful or intelligent. Mashing attack is often the most efficient way to play an RPG as devs don't take time to consider their skill lists or damage formulas. They spend too much time trying to "balance" these things, and not enough time actually striking a balance between the enemies and the player.
I did a lot of things to promote tactical thinking. Namely, wanting to encourage players to use their Skills and not the Attack command. Not that there's anything wrong with using the Attack Command, but it's something I want players to use when they're fighting weaker enemies or have an advantage in using it.
I have three forms of "Attack". There's the "Attack" command which is just a straight "Attack minus Defense equals damage" affair. I then have a version that uses Agility against Luck, and another version that uses Magic against Magic Defense. These each have Elements as well (Strength, Speed, and Magic). Enemies with high defense won't take much damage from "Attack", but might take more damage from "Agility" or "Magic".
Further, most of my Skills aren't strictly damage dealers. Most inflict a state, or are buffs for the player to use, to increase their damage overall. Each skill has it's own Element as well. (I have a lot of elements in order to guarantee that any party composition could win the game if played well, as well as to ensure that players aren't just spamming one attack or skill every single combat encounter to win). Enemies are generally "weak" to two or three elements, "resistant" to 2 or 3 elements, and all other elements are "neutral". My states generally work the same. All enemies (including bosses) have 1 or 2 weaknesses to states, 1 or 2 completely immune to states... and the rest are "neutral". This ensures that players who want to inflict states... can. Even on bosses. Every weapon even has an Element tied to it. Every piece of armor resists certain elements and damage types.
Skills, by and large, will do more damage than baseline "Attack". But, they're not so amazing that you can spam them for each battle. Other skills enhance using the baseline "Attack", or make the skills even more powerful and deadly. It is generally worth it to cast an "Attack Up 25%" skill and then attack.
Furthermore, my enemies are designed to not be "damage sponges" either. They have gimmicks. Things they will use against you. Some of the same tactics you can use against them. By and large, they rarely use "Attack" type moves either. Some enemies (and most bosses) also have a "Revenge" mechanic. That is, skills they only use if you've done certain things to them. Hit the Fire Elemental with a skill based in "Water", and it retorts with "Superheated Steam" against the whole party. A high damage attack that can inflict Burns. Oh sure, it takes a lot of damage from being hit with Water, but you can take a lot of damage back if it seeks revenge. It forces the player to consider that not everything has an "obvious weakness" or that the "obvious weakness" might be a trap. The player can prepare to exploit the obvious weakness, however. If they've got resistance to Water or Burn, Superheated Steam may do very little to them. But, they may not know this on a first attempt.
I even have enemies that will do something different to you if you inflict states on them. I have a boss that if you inflict him with Poison Level 1 or Level 2, he will inflict you with Poison Level 4 as revenge. Now, an "Antidote" cures all levels of Poison, but Poison 4 is quite deadly. It drains 20% of your maximum health each turn.
Oh, that's another thing. My states are pretty powerful. Game changers. consider the contrast from Level 1 Poison which inflicts 2% HP damage a turn for 3-5 turns... to Level 4 poison which inflicts 20% HP damage a turn for 12-15 turns. Especially consider that you can inflict enemies with these states. Level 1 Blind only reduces accuracy by 25%... Level 4 Blind reduces it by 100%. Etcetera. The low level stuff is what you're inflicted with and have access to early in the game, but the high level stuff is what you get hit with later in the game and can use on enemies.
I removed Dedicated Healers as well. White Mage? What's that? Nobody in my setting has any Healing Magic at all. The closest you get is a Cleric who is Immune to most States and who can cure all the states from a single party member each turn. By and large, the player is going to be spending turns using Consumables on allies. Or, using them on allies outside of combat and feeling the pinch in their wallet. So, the player will need to play intelligently and be inflicted with as little damage as possible to save money and obtain more Consumables.
I divorced stats from my Level Ups as well. If you want to grind levels, you certainly can. They grant indirect power. If you want more stats, buy equipment (which is where the largest boosts to your stats will come from) or complete Quests to get awarded with a few stats. In this way, it is more difficult for players to "overpower" the game by mashing Attack... and it's also easier for me to balance an "open world" type game, in that I know about what equipment and stats the players will have at any given time. At the same time, I'm playing with lower stats. Party members start with roughly 10 points into any given stat (though some start much higher or much lower) and roughly 20 HP or so. The first enemies will deal 1 or 2 damage to you each hit. Enemies a little further into the beginning of the game will do 4-5 damage a hit on you if you're equipped properly or have the right stats. If you don't.. they can do upwards of 35-50 damage on you. They are designed around the stats you're meant to have at that point. The equipment you're meant to have. In the early game, you can only raise your HP by 5 points for each Quest. You can only raise your Attack/Defense type stats by 1 with each quest. Equipment will raise those stats by 1-5 for each piece. By midgame, you're gaining 20 HP/MP a quest and 5 points to any other stat per Quest. By endgame, you're gaining 100 HP/MP a quest and 20 points to any other stat per Quest.
Basically, I just have a ton of systems I've created simply to try to make my combat as "tactical" as possible. Things designed to funnel the player into making choices and keeping them from getting complacent. Want to wear the Heavy Armor all the time? Bad idea. Magic REALLY hurts you when you wear Heavy Armor. Want to wear Leather Armor all the time? Bad idea. Piercing damage hurts you a LOT. Want to use a Sword all the time? Bad idea, some enemies take very little damage to Slashing type attacks. Want to use a Magic Wand all the time? Bad idea, some enemies take very little damage from the "Magic" element.
The player has to consider their equipment constantly, their party composition, which skills they're using, if they have to use turns on Consumables, if an enemy may hit them with "Revenge", if a state infliction on an enemy would be more worthwhile than the other skills you have on hand, etcetera. It's all mostly designed to keep players from getting complacent.
Oh, the final component of my combat system? Each skill "Levels up" after completing certain Quests. The player is given two options at each juncture, making a total of 3 choices per skill. Those choices affect how the skill acts in combat and what it does. It can be on either end of the spectrum, or a mixture of both sides. Fire can be leveled up to inflict better versions of "Burn" at higher rates... or it can be leveled up to do a lot more damage. Or, you can take one of the options "in between" so you never get access to Burn Level 4, you never get access to the highest possible damage... But, you still inflict a good version of Burn and do a good amount of damage. Other skills work differently. They are usually choices between utility and power.
The player is asked to make choices. To interact with the world to find out which choices would be the best ones to make. The player is asked to not get too comfortable in their strategies and tactics. They are given the means to succeed and gain ground through clever use of equipment, stats, and skills.
You know what else I do? Expect my player to get Game Over screens. Not just that, but I try to make it happen with boss encounters. If I can't throw every tactic I know about my system at you... Then how can you make a tactical decision at all? Would you ever need to if I weren't trying to make you see "Game Over"?