Is that normal or am i doing something wrong? Do you guys ever get a sore right/left shoulder when placing a fast paced song?
are you playing sitting down?

this happens when im sitting down, my shoulder is holding my elbow up almost horizontal to the floor, and it puts a lot of work on it, so it gets sore quicker.

i find playing standing up, having the guitar not too low down, but low enough so that my elbow is raised not so high, then i can focus my arm muscles in moving from my elbow down, it puts less strain on my shoulder.

i experimented with playing super low, and it hurt my wrist more, and super high, which made my shoulder sore, find the sweet spot in the middle for you, but do try playing standing up, or sitting with a straighter posture,

orrrr, you can put the guitar on your other knee (right handed players, rest gutar on left knee instead of hte right one), a lot of fast players do this probalby for that reason, but i can't say for sure, im pretty sure itll help when sitting down, cheers,

Gibson Les Paul Studio w/dirtyfingers pickups
Gibson Joan Jett Melody Maker
VOX ac30 head
Marshall 1960 4x12 cab
Fender Hot Rod Deville