Arena testing needs to be done a bit more frequently, methinks.
Pale Rider testing shows that they're vicious in unarmed combat with most things, but they're fairly fragile. However, if you don't take them out, they'll get away and recover fairly swiftly with their Healing Rate of like, 10 or 20. It's crazy. However, Storm Dragons and Man-Eaters pretty much lop limbs off with each strike--though it's dangerous, because they're perpetually burning. Also, once I fixed a tiny problem with the CDI tags on the dragonfire emission (renamed to Solar Fire since it's clearly not dragon-exclusive anymore), the Storm Dragon that attacked it literally melted to nothing. It was awesome. Ranged attacks are recommended now.
I might change to just regular fire if I get too many complaints about pale riders being impossible to kill, though.
I found a problem with the treelords, though. Namely, they can't resurrect elves properly. The elf is revived and immediately bleeds to death. This may or may not have something to do with the method of death--namely, combat with a Pale Rider--but it's notable to mention. I also definitely saw the Molten Skin problem.... Also, Elven by-products are occasionally referred to by the creature name and not the caste name. !!Treelord Muscle!! existed from me butchering the elf corpse to stop the spam from happening.
EDIT: Yeah, they still burn to death pretty hardcore from firejets.... I changed DRAGONFIRE to FIREJET and while the storm dragon got close enough to behead the Pale Rider in one shot, it still burned to death eventually. Dragonfire just instantly disintegrates anything. I made them breathe fire a lot less frequently, too--they were set to wait_period of 100, and now they're at 1000. For comparison, vanilla dragons have wait_period 50.