I've recruited members in your situation in the past, so... perhaps this will help.
You have to understand that the natural reaction is going to be as you described. People will be wary of taking on someone with a very 'hardcore' raiding background, and be worried that you'll only stick it out until you realise how 'bad' they are. It's quite a daunting thing for a guild to have someone come into a raid who 'knows it all' and has 'been there, done that'.
However, a good guild leadership team will recognise that having a decent joiner like you may help them improve their raid. What perhaps you are looking for is a solid guild with ambitious leaders who are prepared to take a risk. You need to do your homework a bit about the guild and sell yourself as a match for their guild.
Try and emphasize the aspects of you as a person which make you suited to their guild in particular. No, don't hide the raiding achievements, but don't put them as the highest priority in the application, either. Explain your situation, explain more fully why you think their guild would benefit from you, explain that you're not going to take over or run for the hills when their folks struggle with something your old guild might have one-shot.
Oh, and if you can at all manage it, actually talking to the guild leadership about yourself ahead of an application might soothe their nerves.
It's always abit of a surprise when a 'too good' candidate lands on your doorstep, but it's never an unwelcome surprise! I'm sure you'll find a guild to welcome you in. Best of luck!