I've instanced with others only 3 times I think, first was a pug to DM on my 2 mages, it wasn't great because that was very early on in my MB days and I had quite a few macro glitches (cc particularly wasn't working very well), second was a run with friends, but it was a ruched thing and I wasn't set up very well for the characters I was boxing, so didn't really contribute a lot to the group. Much more recently I ran ZF with my 2 shaman (both as dps because I haven't set them up for proper healing), it went better than my previous attempts, but stuff like making sure my alt is facing the right way and not pipping over when my main got hexxed were not handled by me very well. I was a bit overlevelled for it though (50 or 51) and so ended up pulling agro off the tank quite a bit, but was able to get through without being too much of a pain to our healer (who I think did really well being that they were only level 40 and ret specced). We 4 manned (a dps left after a bad pull led to a wipe) most of it, but couldn't manage Gahzrilla before people had to leave (partly I think due to my toons being in the same place and so both getting thrown in the air and taking a lot of fall damage).

I think it's probably easier to MB in an instance if you have only one role to cover (i.e. dps), I'd like to try healing at some point, but I think that will need a lot of thought to set up so that I can lead on the healer and more or less forget about what the dps is doing (other than pushing the cast button of course). Maybe where I don't MB that often I feel like I'm not performing as well as I should be and I hate being below par in the game (I also hate this if I'm covereing a role solo that I don't usually play and am not comfortable with), but I'd also like to practice and hopefully improve. The last group I had were very good about me MBing, the one that left either didn't notice or didn't care, but the two who stayed were interested in what I was doing and how and one of them added me to their friends list.

I'm rambling... but I think as someone who can't solo an instance at the appropriate level it's nice to still be able to have the instance experience. I'm always a little aprehensive about what people will think of me and if I'll bring the group down/get blamed if things don't go so well. I felt like that when I first started playing the game though, so maybe I just need more experience to get used to grouping on more than one character at a time.