I went 25-50 on MRD in the last couple of days, particularly last night 36-50 in about 13-14 hours. I never had parties before patch so I can't speak for the old system, but at the moment partying seems very viable. Crowd control is not that difficult. Those controlling the crowd are the tanks, usually was a mix of 2 GLA or MRD, PUG could also tank some links. The basic hate moves, Provoke and Flash, are enough to achieve this. If you add a combo to that (on MRD also increases enmity), it's not hard to keep 3 mobs you. With 2 tanks doing all that, crowd control = not a problem. It wasn't uncommon to be fighting 3-5 mobs at once in the strongholds.

Sure, not having spammable AOEs must be slower than pre-1.20, but I don't have that comparison point. MRDs can still use Path Of The Storm + Whirlwind quite frequently, but it might be a bit tricky to start of the combo. It is doable however, even while tanking. With Keen Flurry, it's quite easy to get a WW off at every pull, speeding up the fights considerably. Before strongholds, the mobs didn't really last long enough to have any use for AOEs, so I don't think it's a problem having limited choices at lower levels, at least for party play.

For solo play, however, not having lower level AOEs can be a little problematic, since by leve design you're (almost) always fighting multiple mobs at a time. As MRD I haven't noticed much trouble, since they're pretty sturdy as is and can take the beating, even from multiple targets, but for other non-tank classes it might be troublesome. I don't really know since MRD is my first level 50 class.

Exp parties are awesome. Just my 2 cents.