Personally, I'm with the players usually on editing of base classes, and that opinion is generally spoken as, "If you edit the core rules, it causes changes that were not intended to be changed." Like for example, nerfing spells, removing abilities or feats of a class, etc. Most builders, mistakenly in my opinion, want to take away things, rather than add to the benefit of playing a class to help balance things, and though this is the best policy, it's not always the best choice.
As is the case for PVP modules, where balance is critical to ensure fair pvp combat game play, which would indeed require that certain spells to be nerfed or changed, like Time Stop, Greater Sanctuary, etc, to prevent overly powerful casting combos. (Like timestop, bigby's, then IMGS your opponent to death, or Greater Sanctuary followed by some powerful spell casting to give the cleric a major advantage over their opponent.) Likewise the nerfing of Devastating Criticals or handing out immunities to critical hits & knock down, prevents casters from being completely owned in one round or even just one hit. Nerfing has it's place on some type of modules, generally speaking though most players would probably detest it, and personally I refuse play on servers that nerf everything. (Rest especially)
I don't think the core game is really balanced towards PVP at all to be perfectly honest, though some people dig PVP, it's far more enjoyable when balance is more focused on power, rather than nerfing the heck out of everything, meaning players have access to more powerful items rather than weak items. Then there is the other factor that makes a huge difference, properties on items, which in itself is quite a balancing act as well, for if you give out powerful properties, it can come back to bite you really hard. (Players get use to their powerful items and detest it when they start losing power.)
Even in a base +5 gear system, some classes clearly have an advantage over others, it's really tough to make a Character that is well balanced for PVP or any module to be realistic, balance isn't really obtainable unless there was only one class, everything was "preset", and magic was very nominal if allowed at all. Some people may think -2 to an ability score doesn't mean much, but on the contrary, it restricts what a race can play, or greatly diminishes the power of that class should the player be of said race. (Example a Dwarf Bard, because it receives -2 Charisma, wouldn't be able to start with 18 Charisma, like other races can.)
I always thought TSR did a wonderful job on balancing game play, provided you learn to respect those +2 / -2 adjustments, the benefits of feats, and learn to increase the desirability of a class by adding more benefits to the class, rather than nerfing another class to make it more on par with other classes. It's when put subraces and legendary levels (or other similar systems that allow a PC to level beyond level 40) in a module, that balance becomes extremely difficult to juggle, unless you are great a juggling power, and that would require much experience & adjusting frequently indeed.
If I was to make a solid recommendation, it would be to adjust classes by giving them better benefits, thereby effective increasing the overall "desirability" to play on your module / server, rather than nerfing classes, spells, etc, and then adjust accordingly & revise adjustments where needed. (Players probably won't complain as much if you take something away you recently gave them, but if you start tampering with core rules, that's where things can get a bit touchy & sensitive.)
