Ok that did it I think!!
MORAL:
If you have assigned IPs on your WAN interface outside of the subnet for the WAN IP itself, enter them as Additional Interfaces.
ISSUE:
After activating uplink balancing, its not working
All I've done is set to multipathing and enter the two WAN interfaces... is there some other trick to this? Of course the docs mention no additional steps ^.-
I should probably create another post for this.... or another ticket
Thanks everyone for your input! haha.