My advice is: no matter what the kill order is, make sure to top off the tank(s) some time before the next wave spawns. The final phase is really precarious till you get used to topping off the tanks before your group finishes killing 2nd soldier/knight or 2nd dreadnaught. When the enemy in question is at around 20% or so is a good time to do it that way you just have to adloquium or stoneskin both of them before or right as the next wave pops and you will have a good amount of time before you need to burst heal and it will allow the tanks to establish hate.

If you get caught with your pants down the next phase will pop with the tanks at half hp and you have to scramble to get them topped off, leading to you getting murdered and wipes.