I've got all the UP achieves, for Skadi you want to be by the guns before the announcement, then you have to bounce between 2 guns (only have to move slightly) shooting them alternately, but rapidly. He'll come down after exactly 5 shots if you start shooting right after the emote, and you'll get both achievements easy if you do the reset-room trick.

You actually have enough time to let him fly by twice, so you don't have to bring him down the first pass if you still have adds up - just clean up, put your tank outside (I sometimes drop a earth ele to tank new adds when my tank is outside), and bring him down on 2nd pass.

For last boss, just be sure to have purge on a good key, purge whenever bane is up (and spin your tank around so you don't accidently hit him when bane is up, or turn off attacking or w/e -- I also don't flameshock when he is casting bane). Save lust for the top left box, it spawns little circles that aoe and move and they suck the most, if you lust when he pops it you can burn him down 25% before even a circle spawns.

Its an instance not worth farming imo, I got it down to pretty much a 1 shot and farmed it for a week straight, got 0 mounts and said f** this place and haven't gone back since.