When it' struggling to get on the pipe does it sound really lazy, or does it sound like it's trying hard but not really succeding?
I know it sounds like a stupid description, but: lazy = too retarded, trying hard = too advanced.
Recommended advance for a YZ125 is 1.2mm BTDC. 3mm is a truck-load more (in terms of degrees of crank rotation/time) when you consider the way the piston moves near TDC.
I'd definitely be experimenting with less advance. You might find that you can lean it off considerably with less advance - more power, less dead plugs, etc...