I... don't believe in traditional roles in RPGs. "Oh, it's a tank, it has high HP, high defense, and uses Provoke or Shield Bash or whatever else". I don't like that. I want to surprise my players and force them to drop the (my personal opinion) absolutely stupid and silly archetypes of MMOs.
My tank has exactly one skill that draws enemy fire. "Cover". All it is, is a 3-6 round Substitute skill. It can raise Defense a little as well, to take some of that damage that he's covering for. Okay, so why is he considered the tank, you ask? Every skill he has revolves around buffing party defense or evade, or whatever... as well as using his Defensive stat as an offensive one. He gives the party Evasion percentage (magic or physical). He buffs defense of the whole party for 3 turns. He's got standard amount of HP (no more than any other character), but he's got 3 times the Defense, so he will take hits for you and possibly even keep you in the fight, even if not directly. He can tank some hits and spend turns healing the party with items (I have no dedicated healer class, you must heal with items if you wish to heal in combat or out of combat at all, without an Inn, even funnier is that he doesn't even get a buff to Pharmacology like another of characters, so he's not even the best candidate for handing out potions).
As for your dilemma with raising the targeting rate of allies. I actually gave that skill to a "Jack of All Trade" type character. Basically a rogue. He can use it offensively or defensively (depending on your preference in leveling up his skill". It's called "Threaten" instead of Provoke. If you use it defensively, enemies target him more frequently and he gets a small boost to his Defense stat for 3 turns. But, if you use it offensively... His critical hit rate goes up. Seems kind of weird to do that, right? What's the point of raising his Critical Hit Rate when he's provoking every single enemy to target him? Well, you can equip an item on him to give him a very high rate of Counter Attack as well. Suddenly, he's cleaning the whole battlefield by using his "Provoke" skill and landing Critical Hits all over the place. He can also use his "Threaten" Ability in conjunction with another of his skills that gives him a percentage chance of reflecting magic at the caster. Casts his "Reflect Magic" and then after that, casts "Threaten" and suddenly he's deflecting all the magic attacks to the casters. This character, however, does not have stats to "Tank". They are meant to be used to draw fire from enemies to either use that offensively or defensively.
"Provoke" in this instance is a tactical choice and not what a player should be doing every single turn. I don't like designing skills to be things that are, "this is what you use every single turn no matter what, because doing otherwise is stupid". So, my actual tank character doesn't get Provoke. Meanwhile, one of my Rogue characters does. In this instance, "Provoke" is also a skill that can built on, built around, expanded, altered, played around with.
My point is... Why does that Tank have to draw enemy attacks at all... to be a tank? The point of a tank is to keep everyone alive, right? Or, make their chances more survivable. Granted, it's the easiest way to make the tank keep everyone alive. Easiest as far as programming is concerned anyway. Lessee... 3x HP of any other character... 3x Defense of any other character... Give Provoke skill. Give Sword and Shield. Bam. Done. Boring. Typical. Easy peasy lemon squeezy. Nearly everyone designs a Tank this way. From AAA to Indie devs. To JRPGs to MMORPGs. Why not differentiate your Tank some?
That being said... If I have to go with the boring "default" archetype of Tank character with the boring and "Default" Provoke skill... I prefer it just make the Tank targeted more instead of "enemies only target the Tank", because at least there's still a chance someone takes a hit other than the Tank and battle doesn't feel so... Easy Mode. But, I like a little strategy in combat, a little bit of randomness, a little bit of "you can't prepare for everything, but you might be able to react well to something you didn't predict". Most combat systems rely on players being proactive about 95% of the time... and restarting the battle after losing the other 5% to be better proactive in combat. I like my combat to be half proactive (you prepare for combat before it happens, you know what skills to use against specific types of enemies, you have strategies planned out ahead of time) and the other half... reactive (the enemy throws something at you that you didn't expect, they get lucky and wipe someone, they use your tactics against you, they throw a wrench into your usual plans of combat, they do something you had no way to prepare for and even a restart doesn't make preparing for that easier, etcetera). Combat remains interesting and engaging if you cannot negate everything an enemy does... or most of what an enemy does. It engages when it teaches you things and punishes you for complacency.
My advice about a Tank character with Provoke is just to see what else can you do with it. My answer was to say, "How can targeting this character be useful other than just drawing fire?" and that giving Provoke to a Tank was too overpowered and broken if I designed the Tank in the usual fashion. I rolled with that answer. Maybe you'll find a different answer that works better for you. I encourage you to try new and interesting things. Play with all the tools at your disposal in the Engine. Did you know that you can make a state "Contagious" to others in combat? You can really do some fun stuff in RPG Maker if you look at it.