I will also say... fairly recently I have played a straight up mercenary combat machine in a different system (DragonStar, which is d20 in space, dragons rule the empire). The group is level 11 now, and my character as a fighter a) has a ton of feats, b) has a ridiculous to hit bonus and c) has excellent armour. None of the others is really a fighter type at all. Due to a variety of specialisations in automatic weapons fire, if she clears the opponent AC by 6 or more, my character is now capable of spitting out 12d10 damage with an attack, and at 11th level that's 2 attacks per round. Even though I choose to self-nerf and use a less powerful weapon, she is still capable of 10d6, twice a round. (self nerf chosen because otherwise the GM would have used similar weapons against us, and I couldn't survive a single round of that damage output)
There isn't a huge amount that can stand up to that kind of onslaught. Kraken - 1.5 rounds. T rex (at a lower level) 2 rounds. So the GM tried to compensate but giving us tougher opponents. But we found out that an opponent capable of giving my character a run for her money, would make mincemeat of any other character... so in order to avoid TPKs, my character essentially had a big target painted on her armour.
Which is all well and good... but in combat, my combat rolling took as long as the rest of the party put together, and I could see they were getting annoyed at being second raters. End result is that now, no one wants to play in that game any more, myself included.
Ther moral of this tale being, be careful how you balance, it might have long term effects which are difficult to come back from.