Hello!
I had the same problem as you. At lvl 55 with decent items, I just could not resist very well, not even in SD2, let alone in SD3.
So I decided to go lvl 60 and benefit from the Phoenix Shoes and the lvl 60 helmet (both with block bonuses).
My character is warrior AURA. I have P Aura and G1 Berserk (but I dont use berserk when leveling the pet in SD3 as it increases the damage I receive). To compensate, i use Green potions L.
I have around 17k HP, 80% Arachnids, +8 Fear Mask and Phoenix Shoes, around 20% absorbed by HP, lvl 40 shield with extra 10% block and 20% EXP. Also, FMS with 43% avg damage and 10% arachnids. My buff has G1 Blessing and M7 Crit.
To summarize: HP, block bonus (shield + phoenix shoes+ lvl 60 helm), % of damage absorbed by HP, arachnids bonus, imune on shield, stun chance (if possible) and Large Green potions. Also, P skill on main and at least G1 blessing on buffer.
With this setup I can tank 1 full room at a time in SD3 (i dont stand in the centre. I noticed that staying close to any pillar tends to be better and more efficient that dragging the spiders in the corner. This way i do less moves when going from room to room).
I wrote this so you can have an idea of what are the stats/equipment you should aim to, if you are a warrior aura. Weapon suras may have an easier life.
At the moment, my pet is lv 93.
As for exp rings and stuff - best combo is IM exp ring (that lasts 1 week, whether you are playing or not) + EXP ring (30 minutes) + pet exp ring (1 hour).
Good luck!