Raiding with the standard UI

Q u o t e:
I'm curious, if anyone raiding on a daily basis using only the default user interface ? I'm not saying without add-ons, just with the default UI ? How does it work for you ? I tried several UI add-ons but there is always something missing or annoying features i dont need, i just havent found one i feel confortable using.

I've done it before with only a couple of add-ons strictly for side information. Like you said in your post, it's about finding something that is comfortable for you. I've used a variety of add-ons in my time playing, but in the end, I like having the least amount of add-ons I possibly can and it also helps me keep track of the current functionalities we have with the UI so that I can better speak to the developers on feedback for it. Our UI team works very hard to find ways to improve the functionality and at the same time keep it as accessible as possible to as many people as possible. They also do a great job in keeping the accessibility there for mod authors to create add-ons that make sense to those that want to use them. It's a win win situation.

Q u o t e:
Any healer using the default UI is just going to be a bad healer.

This is patently false. I've never had issues and have gotten plenty of compliments. A good player is a good player period. If you are a better player with mods, then use them. If you're better without them, then don't use them. It's always about your own personal play style and what you are most comfortable with. There is no one option despite what some may say.

Once upon a time, when FPS games did not have all the functionalities they do now, I would spend hours refining just the right configuration. As the years have gone by and gaming has advanced, I've found those very things that I and my clan mates spent so much time working on are now the standard. The same can be said for the improvements to MMO interfaces. I've gotten by on less and have far more with the standard WoW UI than we ever had in the past. For me, I'm comfortable with it as it is.

These sorts of blanket, "you're bad if" statements are destructive in nature since players are individuals and not identical or rubber stamped copies of each other. What works for one person isn't always what works for someone else and it's important to keep options open where possible.