Spider strats:
1. AOE Nuke. Works best for low levels like what your on, but your almost to the HP burn strat thats much better and will last you all the way up.
a. use all AOE champs with enough support to keep alive.
2. HP burn strat. Works well at mid all the way to 20. easiest strat imo.
a. use a negative affinity spider tank. Spider 12 is Green. Use a Red, defenseive champ, to tank the spiderlings. Your Doompriest can do this if you can build her with high def/spd/HP. I wouldn't worry about resist on low levels unless you can really pull it off. you probably cant. BEK is also red so make her HP much higher than the spiderling tank to avoid her getting hit. APO and BEK keep tank alive while the HP burn kills the spider for you.
b. Mute Trundas damage. She can not be an HP burner and a Nuker. They are counter productive. In HP burn strats you will try to do as little damage to the the spiderlings as possible. This keeps them alive to BURN the boss. If you have enough TM reduction on the boss, you can HP burn right away, if not wait for the first boss turn then do it. She will need more ACC and SPD to do this job.
c. Apothecary- no need for accuracy or resistance. SPD/HP/DEF and crit if you can, but not needed. High def because APO can be your affinity tank on red levels if needed.
d. Do not use Royal Guard until end game and your trying to pick the speed of clearing up. Replace RG with someone like Armiger. He will keep the boss TM down. Felhound in a stun set would be an ok choice to CC the spiderlings if your affinity tank is taking too much damage.
e. Coldheart. High HP, ACC, 70% crit, Spd and rest into crit damage. DO NOT build attack. ACC>damage. Her first job is to deplete the TM. This requirs acc and staying alive. Second job is nuke.
F. Armiger. Easy to get. Spd/Acc/crit/HP.
3. Speed farm. Highly gear dependant.