First of all: What does rune of giants jump attack scale off ?
My idea was to build a wiz 3 > thauma 3 > rune caster, full int to get max con with transpose and use rune of giants to get crazy HP numbers and still do some damage on auto’s.
Any experience with this ?
Jump attack damage = Autoattack damage.
Why would you need crazy hp numbers if you can’t use any skills as a giant?
To be a giant stomping on people.
@edit: power staff /cafrisun set works with the jumps ?
I have neither, so no idea 
Hello, the damage used is from your main hand, so for a wizard, based on your MATK, and if you use the rune for a swordman, based on their PATK. Here are some numbers:
Regular Auto-attack
GIant Auto-attack
Giant Stomp
I’m using the Sacrament buff, which works like Cafrisun set, so yes, it works for the stomp.
You have a fun idea, but I really can’t recommend Rune Caster unless you’re a cryokino.