Well one lesson I'm learning here is that ... there is no real point in boosting the power of the PCs if you are boosting the power of the monsters too. (we use the Dungeon Dude array and generous HP rolls) - I mean part of this is inexperienced and enthusiastic DM energy (I repeat, this is a fun game), but this game has made me realize how there is no "point" in boosting PC power (beyond say, fixing a class/subclass that is seriously under-powered).
Another lesson that the GM may or may not learn is that having super deadly battles but at the last second pulling your punches and having allies save your bacon is, uh, weirdly anticlimatic.
Lastly, I will note that this semi TPK (we lost 2/4 permanent PC, the 5th member is only there half the time because of scheduling) is seen by our GM as just another opportunity for high adventure. I don't know what he's planning, but he's been dropping hints about Spock's resurrections in Star Trek so...
For me, I will take the opportunity for my character being brought back to life to have a "change of heart". the real-world reason I didn't play a rune knight in this game is because someone else had played one in the previous campaign and I wanted to try the psi warrior... but really, the RK is better/more thematically appropriate. The RP angle I will take is that my character, a scholar who studied giants extensively, rejected giant ways because of what they had done to him (almost all the PCs are from a small town destroyed by giants a number of years ago), but now he realizes that runic magic is the key to victory - and to truly understand the Giants.
I'm not sure what the ranger's player will do. My character's body was saved, but the ranger was being used as a chew toy by the dragon as we fled...