Q u o t e: Again, "don't like it don't use it" is not a good reason to include something.
True, but adding something fun to the game is.
Q u o t e: Otherwise what's the keep Blizzard from adding an invincibility button? Don't like it, don't use it.
Game breaking balance and exploitation... bad example. You're again not looking at what it adds, focusing on irrelevancies.
Q u o t e: If there were mercenaries, not using it would cause a major loss in character strength. "Don't like it don't use it" only works if the player has Alternatives.
You're whining about a problem you see and want to scrap the whole concept instead of making suggestions on how to address the concerns.
I'd say that when you have a follower the game's difficulty could be slightly ramped up (as is the case with D2's /players X), but without additional rewards (loot / experience). The alternative would be to play without a follower, with the same reward balance, but without the extra difficulty.
In PvP, simply have a setting for each battle on whether followers are allowed.