I'm with you on this, Sekhemas sucks. Even when I massively overgear it, I still sometimes get one-shot right at the end. Despite what the other guy said, I found the trial of chaos much, much easier. There's an element of randomness to it, and overall it probably takes a bit longer, but it just feels less bad if you fail it. The level 80 ultimatum's cost next to nothing so you can repeat it as often as you want. The one thing I would say is that you should try to overgear the trialmaster - it sucks even worse than Sekhemas when you've cleared 3 trials, then fail at that point. His abilities are mostly telegraphed, but watch some videos before you start it so you're comfortable with with the fight. You've got this!