Yeah, I can see why 19 would be a pain, with so many of your key champions magic affinity...
Maybe try Scyl, MM, Robar, Coldheart and Visix, on manual, with enough resistance on the spiderling target and try to keep everyone up until CH can finish her job. MM's shield should be fully booked, that helps a lot. Robar isn't ideal but you do need some kind of def down and I don't see a lot of alternatives - on stage 20 you could bring Royal Guard instead but on 19 he'll just get targeted and die. Visix isn't great either but should help with keeping the turn meter down - and reduce the spiderlings' attacks, as well.
I guess on manual Visix (200+ accuracy will suffice instead of armiger). You only have to beat 19 once. With enough speed Visix and CH could keep main spider from getting turn. MM definitely needs to be booked and fast. Possibly
HK (lead)
MM
Visix (use aoe dec speed 1st, then A1)
CH (use a3 1st)
Apothecary (Armiger at 50 would be perfect, might actually work to get visix enough turns and CH back to A3)
Raidernation32 - this is my current clan boss build, for the level i am ive historically had a poor team set up (one of things i havent really focused on) but looking to deal 100m to clan boss to complete arbitor missions! this team below is a missmatch probably- Elenaril is my main damage dealer, but i havent built septimus for clan boss properly. the team below are doing around 7.5-10M damage max
Spider 19 is the hardest Spider Den level because it's Red affinity (when at that point, most players have Blue affinity)
I remember it was the longest Spider fight, like 10+ mins. You will need a champ to revive ally multiple times, with very high resist, as long as he/she survive, the whole team survive.
Hey JC
I posted an update to an earlier post of mine asking for help with speeds. Thought it best to post there instead of on your Spider post.
Keep in mind, I am not expert on these UK comps. Thankfully I have a great Clan that helped, um more like pushed, me to get the team set up. We are on abouty 4th week of 2x top chest in UNM.
This is the title. You can ask me more questions there if you like.