Help with Gemling legionaire End boss build help

Hello, I am fairly new to the PoE series. I have a level 93 Gemling Legionaire Tempest flurry/stormwave build. The other night I was invited to do a super breach where you go and fight a super unique i guess. Well during that fight, within a minute I was completely out of MP and was losing HP fast. I eventually got 1 shotted by the hand. I also did a simaculurm or whatever and also died there.

My build is pretty decent, with dex at 500 int at 500 STR is 275. RES is 74/75/76/14. I tried to use HP leech jewels but it seems to have no effect on tempest flurry.

Does life leech and mana leech actually work for tempest flurry? I have looked at a few tempest flurry builds on mobalytics and maxroll but those builds are for clearing maps not doing unique bosses.

Any tips appreciated. Thanks!