What team are you running at the moment?  After about spider 15, the goal is less about pure damage to keep the spiderlings down, and more around control and HP Burn.  In other words, you want to get HP Burn on all of the spiderlings, and then freeze/stun/sleep them so that each time they take a turn it triggers the burn on every enemy.  If done right it will chunk down the boss's HP very quickly.

Also, which stage are you running on auto to farm?  It sounds like Spider 19 was a struggle so I assume you run Spider 16 or something?

You are missing a solid leveled AoE HP Burner, though you do have Drex.  Drex is also the weak affinity for Spider 20, so could be built in a way to ensure he is the target for spiderlings, so there might be an option around that.  You also have Ultimate Galek, though he is only level 40 at the moment so would need some investment

The other question I have is around your gearing.  Your screenshots are showing your Visix buid which only has +42 speed.  This is very low, and it sounds like you aren't using speed boots (which would be giving +45 speed by itself).  If all of your other champions are built in a similar way then you will struggle with content.

Unless there is a very good reason, all of your champions should have speed boots.  The faster a champion goes, the more often they cycle through their abilities, and the easier the battles are.  

Gear in particular is going to become much more important once you start to tackle stage 20+ for the dungeons.  If the best banner you have for Visix is a green 5 star one then you might need to do a lot more runs on the earlier spider stages to find something better.  This game does become a bit of a grind in that you really want to be running stages like Spider and Dragon quite a lot to get decent gear

Basically what rose said. Team I would use:

Drex - spiderling tank

Visix - only a1, tm control

Armiger - only a1, tm control

Steelskull - heal drex

Ninja - cc spiderlings, but make sure to select a spiderling before he attacks so that he freezes. If that's too annoying for you to do, use scyl instead