Timely Death

This is one of the easier damage rush achievements, since it requires a paltry 1068 average DPS from your four non-healers. Even considering the movement requirements, that's easier than say, Good Grief; that requires 1798 average DPS between the four. The only challenge would be ensuring your group's tight movement in and out of Lightning Nova.

A well geared group with a strong AE healer could also simply stand in the Nova, reducing the challenge significantly.

This achievement requires you to kill Loken before his third Lightning Nova, basically. If everyone in the group has at least 16,000 hitpoints, this achievement won't be a problem. You don't need a priest or a druid either. Naturally, the fight is meant to be done in a specific way. You're supposed to run away from Loken as the Lightning Nova commences.

However, due to the way his lightning pulse works (the further you are away from him, the more damage you take), in order to do this achievement, you're much better off getting some nature resist (don't gimp yourself with nature resist gear, just get mark of the wild, or a nature resist totem, or nature resist aspect) and staying in for the lightning nova. After the nova, everyone gets topped off over time, and DPS continues. He should die shortly before or after his second lightning nova.

The reason you won't want to run away is that, while you won't take the lightning nova damage, you will be losing DPS time running away from him, and back to him. If you run away and back to him each time, that's ~20 seconds of non-DPS, and you only have 2 minutes to kill him, not to mention that you'll be taking damage from his other lightning attacks as you're running back to him (which, given how far away you are from him, will do a lot of damage).

Lucky now with MoP out, if you have any high level character you can kill [npc=28923] in seconds if not a second.