Good  morning,  I  could  be  biased  here.  But  I  would  use  santa  over  MM  in  spider  for  the  unkillable  and  shield.  

I  don't  have  a  santa on  my  main  account  so  i  don't  know  if  he's  better  than  MM

i'd replace roshcard over mm. roshcard is a great champion, but he doesn't really bring anything to spider besides his a3 (and his aura, but venus and nicholas offer the exact same one, so it's redundant in your case). mm, on the other hand, offers a shield, cc, and ally protection, as well as a little extra healing if you gave him the harvest despair mastery.

On the whole, i'd say your teams are slow due to a lack of offense. Your teams are all made up of support(esque) champions with only one or two attackers. While you're still climbing the ladder it's a pretty good strategy to use, but now that you're at level 20 it would probably be best to figure out who contributes the least and drop them for someone more damage-oriented. From the list you gave, i would recommend royal guard as a good starting point.

You should build an unkillable cb team, do you have doompriest? If not grizz jarl will suffice.  Alure for FK. Where are you in arbiter missions?

I  was  thinking about  Fire  Knight  set  up with:

-  Catacomb  C.

-  Cupidus

-  Venus

-  Alure

-  Sycl  or  Rector  Darth

I'm  not  sure  how  it  would  do.

You  could  have  Cupidus  in  Stun  set.

You  could  have  Sycl  or  Rector  Darth  in  Shield  set.

I  feel  like  it  could  do  ok,  but  I  don't   know.

I  don't  own  some  of  heroes  you  own

I  think  he  is  running  a  Clan  Boss  team,  but  not  the  one  you  and  I  run.  I  think  it  is  one  of  them  that  doesn't  need  a  cleanser  and  you  can  use  3  dps  in,  there  are  three  different  comps  I  think.  Like  Fast  Skullcrusher,  Tower,  Fast  4:3  Skullcrusher,  Tower,  and  I  don't  remember  the  last  one.