I have a mixed feeling about addons.
WoW is almost unplayable at advanced levels when you go in naked. Deadly Boss Mods and damage meters are a must as are mods that change the UI. Raiding Guilds used to ask for screenshots of your UI to be sure you were modded. It's a bit silly and...I think DBM has ruined my ability to play this game. How do I move out of AoEs without a sound blaring in my ear? I'm having to teach myself to rely on visual queues only after a long time of heavy reliance on audio ones. Honestly a part of me would love to have a DBM and a timer addon to help me manage BLM a little better but I shouldn't NEED such things to play. If they became available I'd need them because you are just crippling yourself without such things.
Damage Meters are.... How to discuss damage meters. Any DPS would love to have a live parse on their screen telling them how they are doing. It helps you tighten rotations when you know exactly what you're contributing to a fight. The problem is meters change the environment of playing a DPS especially in a PUG. Whereas before you were a united front against a boss now you are engaged in a competition with everyone around you to not get kicked from the group. This attitude has actually destroyed the self esteem of some WoW players. I know some players who came here, tried their best, and kicked themselves if they felt they were underperforming (heck I do this). One person I know tried healing a Trial for the first time and after seven wipes she was in tears and had to leave even though the rest of the group was trying to encourage her to try again. It's hard to feel good about anything when MMO addons have taught you to see yourself as a number and nothing else. You know how people in FFXIV will usually attempt something a few times before voting disband? In WoW people usually only have one attempt in them. If the numbers don't look fantastic they will leave, to heck with people who've never done the content before (they're usually vote kicked anyway)
If SE allows addon support they will have to be careful in its implementation. I worry addons could change some things about the community. They are great tools but tools are all they ever should be.
That was probably a rambling post, sorry, never had my coffee today.