[Lewdcifer]

Crawling spikes being able to achieve triple damage is undeniably unhealthy, considering you can set up 2 ice points a turn on ice and still have 4m left over to take an action with. I would very much like to see this capped at 100% Extra damage instead of 200%.

This is true. Crawling Spikes can get really strong with an easy enough setup. It pelts even through over 60% Magic DR with damage values that shouldn't really be seen in magic damage tanks. I agree that it needs a nerf, and this proposition should (hopefully) be good enough.

Rapid Kick is a whole 'nother story [...]

Note this was done on a tank, with the buffs mentioned in the original post plus impure element. That's 509 damage - usually approx. half of an average tank's Maximum HP.

I don't really know what the proper approach here would be, but this screenshot should be proof enough that Rapid Kick needs to have a decent damage decrease or a cap on how much damage it can do.