They would help a lot. Endless Hail with poison inject/venom arrow would help tremendously. I love venom for the ranged interrupt but poison inject can hit 20k crit below 50% health. Between those 2 you can kill 2 crystals at the same time. Do you ever run bloodspawn test?
What's the issue with the crystals? Getting knocked down? I had this yesterday, someone said there's a rock that moves you hide behind so you don't get knocked down.
I haven't tried since, but it's what was doing me in all the time. Getting knocked down then having to fight a crem guard again. Either the boss aoe killed me or dodging it meant the crem guard killed me.
I have 35k stam. 900 regen 4.7k wep dmg. 17k health. I'm definatly considering not trying it ever again
My stats on my Stamblade are a bit different than yours. My weapon damage is lower, around 3.9k, higher regen (~1200 + Siphoning Strikes), and higher health (~19.5k). My crit is around ~65% and I'm using trap beast and Shadow Mundus to boost crit damage. My best score with these stats is ~530k.
Don't give up! Take an extended break until you feel like challenging yourself again. My friend recently did this after focusing on Trials for awhile. He went back in and 1 shotted the whole thing.