Your whole argument is based around you don't want to use an ability because when it's done casting you don't see the boss taking damage. Unless you are in top 10 world guild, I highly doubt damage is the main reason you wipe. But I can see hundreds of times in raids where another person throwing a heal on the tank every 30 seconds or so could really help on certain bosses.
My mind is blown by how selfish people can be in this world. Oh I'm a dps so I shouldn't have any other responsibilities is stupid. Do you realize how bored of this game you and most people would do is just sit there and do damage and nothing else. It's the difficulties that make a game fun because the obstacles are constantly changing for you to adapt to. That's why I play WoW because each time I go into a dungeon or raid something changes and that means I have to be able to change in order to play, the day I got into a raid and it's the same thing every time is the day I stop playing WoW.
But clearly change is too difficult for people to accept because it means they have to learn something new, and god forbid that means I might not be good at it straight away. Welcome to the real world where you don't always get what you want, and have to work with it regardless.