I didn't have any issues with XP gain at all, and I ended up being about a level and a half to two levels above the MSQ before I hit cap and the quests themselves started catching up. I did the entire MSQ on RDM and did a little side content. A few FATEs here and there when a bonus XP one popped up while I was near it. I also did the aether currents and flying quests, along with map completion and lookouts when I saw them. So nothing too extravagant. I did have at least a couple weekly challenge bonuses pop while doing everything and had a bunch of rested XP to burn through as well though so it wasn't just plain, unaugmented MSQ XP and nothing else.