Mate, you are pushing that green bar in a wrong direction...

 There is a problem in games, that I want to discuss.

Heal in PvP.

Cons:

- No natural mechanical counterplay (or you have to invent counterplay), most games can introduce only tactical counterplay to heal (burst damage, focus healer).

- Too long combat (can be infinite, in some cases)

- Lack of feedback in some cases (why am I not doing any damage???)

- Problems, caused by "solutions" (oneshots, artificial. hard to understand mechanics, such as heal reduction)

Pros:

- You can shout "Focus healer!" if you playing with voice communication.

In resource managing gameplay, which many games have in, at least, some sort, health points of a character is a foundation. I mean, name a game that don't have health points, or hit points of some sort?  We are raised in the concept, where when a green bar of health points comes to mark 0 - character dies. That means, that you, as a player, crossed a line, designed by a game developer... Well, come on, everyone knows what is Hit points are, and why they are here.

Someone, very long time ago, thought, that it will be a damn good idea if one player can replenish health points of another player, though that player could withstand more damage.

Good, now we can show to the player that he is powerful, look: you, guys, just slaughtered that dragon, it was very powerful, it had 10 times more hitpoints then your generic tank character and been capable of 10 times more damage than your generic damage dealer character, you are so strong. Oh yeah, that was possible, because you had a generic healer character with you, who was pushing your green bars all the fight, back to the top. That's quite fair when we are talking about PvE, but what about PvP? Problems started, when someone came out with a bright idea, that characters can fight not only monsters, they can fight other characters, controlled by other people, with exactly same rules and mechanics, as in PvE setting. 

Everyone knows about balance rock-paper-scissors concept. But, (remembering famous WoW meme) what about mushrooms? Suddenly, you can not balance your game at all, because there is this guy, who pushes green bar to the opposite direction, he is undoing the damage players do to each other, converting what was a fair fight, to the endless torture, where DD's can take more damage then tank and tanks became totally unkillable, yet useless, because they can not overtake all those heals! Of course, I am hyperbolizing, but you probably can recognize a few games that suit the description. 

Yes, you can bring some ideas how to fix this mess: implement burst damage, try to balance the numbers more carefully, invent heal reduction, etc etc. That all is nothing but canes that you need for your lame gameplay to be able to stand and not fall down. But then, you will need canes for your canes, because burst damage associates with "oneshot" problem, and too much heal reduction is making all healing classes (which are the root of a problem) useless, etc, etc. And yes, how could I forget, you will need a healer in each team, or you will have huge (well, maybe not huge, but some) matchmaking problems (if you have it in your PvP game). And the other thing, heal mechanic (i mean the amounts of heal compared to amounts of damage) does not have good counterplay, so you will need more canes, to implement that.

So, probably, you can see a picture I'm painting.

- But Sergey, you would probably say, - you are just hating healers for no reason, we know all the problems for decades now, we have huge experience how to deal with them, and even, who are you to lecture? And you don't even offer a solution! We have a large group of players who enjoy playing healers, because they care about other people, and tend to make good, to keep other people alive!

Well, that's not true. First of all, remember, we are talking about PvP game. And those who play healers (probably, not all of them, maybe just a tiny part, ok, its just me), are keeping their teammates alive so they could enjoy the slaughter a little bit longer, like a little sidekick of a villain, who is laughing, watching at his master is making others suffer, but too weak to inflict suffering by himself. Believe me, I'm playing as a healer a lot.

And second, I can offer something, I will get to that point, just a little bit later.

First, let me explain, I do not think that regeneration of hit points of any sort is bad. Heal can be good if done properly. What is bad heal, exactly? That's easy. Heal that has ruffly the same influence to the character as damage, it can receive in the gaming process, is bad. It should be avoided in games with a possibility of PvP action by all costs. What about regeneration, heal over time, and other stuff, that can not overtake damage? You definitely can use it, but carefully. But everything, that can undo the damage with the speed, comparable to the speed with that damage was inflicted, is a bad solution. It steels the dynamic from gameplay. It lacks feedback.

So, what are my propositions, what can replace heal?

1. As a first solution: don't make heal. At all. Let characters die with honor.

2. If you desperately need a support class or anything that helps friendly characters to stay alive longer, think about preventing damage, not undoing it. This can be many things, and in past few years many of them find implementation in games, like shields (buffs on players that can withstand some damage, then they fall off), if your damage is done by any projectiles that have travel time - player placed walls that block those projectiles (bullets, spells, whatever).

3. You can even split your health bar in few sectors, or make multiple health bars, only one of which can be "healed" (this solution is often used in arcade games in a space setting, or in other futuristic settings). I would not call this best solution, though, because it does not solve a problem, it just makes it smaller.

That's all for now, be creative and don't do bad mechanics in your games.