I agree with most of what is posted here. My guild downed Mimiron for the first time last night (25 man) and we consistently made it to phase 4 before that. Use cooldowns for the plasma blast. Its easier when you have someone else do it. Ours is typically like this
Pally CD first
Pally CD second
Pain Suppression/Guardian Spirit (if you have a 4th, but you shouldnt)
Keep Last Stand for when someone screws up or goes late. Since the damage ticks, if you hit yellow with one tick and red with the next, you will need LS to make it.
For Shockwave, my experience is not to intervene. Someone could move out of range or they could shift to put a mine between the two of you. There is plenty of time to run out. He always shockwaves after plasma blast so I set up my camera facing away and pick my path. The moment he emotes, I hit both mouse buttons and Im out.
You can actually charge back in right as he blows up and not take damage. If you do this, you keep him in one place which makes the next set of mines overlap the previous ones. If he moves significantly, the next set could create an "Olympic Ring" type scenario that is unpleasant.
Deeps for show..... tank for dough.....