According to the rules as they currently stand, it is impossible for the beastman lord to win the game if the heroes get to the keep and one of them is playing whatsername (the girl with ghost and fly) since the avatar is incapable of targetting her. The same applies to the titan if she has grapple.

Similarly, if I'm not mistaken, the spider queen cannot harm any hero who is immune to web.

I've seen a few different house rules to handle this (and many of those suggest applying the same rules to named monsters) but I think it would be important to get an official ruling on this.

Spider Queen: her web strands are not Web tokens per se, and they don't inflict web on the figures they touch. Basically, immunity to web has nothing to do with her.

Titan: The penultimate faq removed Bear Tattoo from RtL

Beastman Lord: I think it's on the list, but I'll add it to the balance issues if it's not.

I wonder if just making all Avatars immune to Grapple would be a better fix than removing Bear Tattoo from RtL?

I'm not sure: KW has repeatedly said that it would take a significant situation to get him to agree to negate any hero's skill (which is why familiars can cross pits and follow their masters). On the other hand, Avatars are a "significant situation".

If the Sorcerer King gets an ability that negates all surges, thus possibly negating three skills and Landrec the Wise's power, then I think it's fair to make Avatars immune to Grapple, given that Bear Tattoo also gives health.

A simple enough fix for Xyla would be to change her Ghost to Stealth against named melee monsters.