Wow...deja vu
I posted my response to this over in the Lua forums at lotro.com, but I'll run down a brief synopsis here, just to cover my bases (as the OP did
)
Yes, Palantir could be done more efficiently when it comes to updating, but make sure you have the latest version - just to be safe. There was an update not too long ago that really destroyed frame rate, as I was trying to handle a Lua/LotRO graphics quirk, using a very very bad method.
But, to be honest - other than after this patch, this is the first complaint I've gotten involving frame rate - not to say that you're somehow doing it wrong, or that you're wrong, because you don't have more people backing you up - but when it comes to priorities on updates, if I don't hear about it, I'll assume it's not a problem.
Like I said, there is some definite room for improvement on how, and when Palantir handles screen updates - but it isn't entirely update events that are to blame - but rather if there's some form of graphics drawing taking place during that update. Since Lua graphics are not hardware accelerated, every time a graphic is drawn - whether that be displayed, hidden and shown, moved, animated, etc - causes a much bigger hit to your FPS than the rest of the UI will. Especially when you're creating multiple elements, or repeatedly hiding/displaying a graphic.
That being said, due to the nature of Lua graphics - even if a plugin is written to efficiently handle events - plugins that use/manipulate graphics are bound to cause a hit to your FPS. How much of a hit depends on the system.