In War on Iokath, at the finale fighting the Sentinels they got rid of the Stomp trick. The Sentinels are now immune to Stomp damage. You can no longer stomp them to death quickly. They remain almost impossible to kill them all, and a dead one respawns if you take too long. However, I figured out how to defeat them. It will still take forever and you will die, but for me it worked. Move your walker so that you are in the same space as one of the Sentinels. That will prevent the Sentinel from damaging you. From there focus fire on one Sentinel at a time with Missile Keys 1 and 3. When you die use the medical probe to remain to keep the instance. After healing go back to a Sentinel space to ignore its damage and fire. When you have just the Sentinel you are on left then you can move and face it. You do more damage to it then it does to you. Hopefully you won't die before you kill it, but can do it when you respawn. You also have to hope a dead one doesn't respawn, but following the same space trick will buy you time.

It used to be if you opt for the going back to the medical tent to heal will restart all three Sentinels. However, when I did it out of frustration during the learning process since I did not want to wait three minutes for the probe on my third death, when I got back the dead one remained dead, so maybe it won't matter which respawn method you use. The combat remains a fuctercluck of unfun, but it will be defeated eventually.

I really hate they got rid of the Stomp trick though.

An update. Before playing this again I upgraded my armor from leftovers of other characters 280-312 gear, mostly 312. My overall gear rating is 306. One thing I noticed when setting up the turrets, gates, etc. the enemies were not deadly. Usually that mission for me is like old Spirit of Vengeance. I die, die, and die again. I get it done but keep dying. Not this time. The enemies barely scratched me. Gear must really matter.

As for the Sentinels maybe it was the gear too, but they were relatively easy. I did the trick of moving my Walker to stand on top of one. I focused fire the 1 and 3 laser attacks with an occasional 8 button missile against one Sentinel. I was barely at quarter damage when it dropped. I did the same with the other Sentinel, dropping it with me at about half hit points. I then moved off the Sentinel I was on and repeat. I killed it without dying, and there was no respawn. I don't know if the designers weakened their power for Story mode, but for now I'm thinking it's the gear. I'm glad this time it was not a fustercluck getting it done in a few minutes to play on. If it is the gear I'll no longer dread playing War On Iokath now that I can give my characters hand me downs.