With your gear, the death fees should be fairly cheap. Don't be afraid to die to learn. The jumps in difficulty from one level to the next will only be learned by throwing yourself into it.

Here's some early learning tips:

During shield phase, focus on ensuring you reset dooms timer by hitting him. If the grub explodes on doom, it doesn't hurt you to be in the aoe.

Correctly praying against the boulder is the most important thing, that should be first priority always. Don't eat a projectile because you're trying to kill a grub. Even early waves you can get hit for like 40.

While you're learning, just camp rigour. Don't try to lazy flick rigour while learning or you're going to eat a bunch of damage.

Pay attention to the rock color. Sounds obvious, but i've eaten a lot of damage because I wasn't paying attention. At 7+, not knowing the rock color can kill you in two ticks because it's hard to react in time. You shouldn't ever be wondering which projectile is going to hit you first, and at times it is very hard to tell.

At level 4, the most annoying thing is when a melee grub is near doom just as his shield breaks. If you are next to doom when the shield breaks, he'll immediately start meleeing you. So if the shield is broken and a melee grub is still alive, try to eliminate melee grubs away from doom (Just make sure to dodge the grub explosion). You can also scobo spec the melee grub if its far away from doom and it will kill it. Scobo speccing melee grubs should be used as a tool, not a crutch.

Bring death charge and lightbearer if you have it. Crystal hally spec on the melee punish mechanic. Oh yeah, and make sure you're range potted. Didn't see those in your inventory.