I'm having a hard time deciding on who to take tobrank 5 (4*)

I use BW For war (attacking). I don't think she needs to be rank 5...I mean, I don't think her damage will be increased by much. After 12.0, seems like she isn't as strong anymore.
Ability
41- AV
99- BW
42- cDD
99- HE 4*
40- elektra
48- WS
21- punisher
I'm open to taking my karnak to rank 5 (currently at rank 1) . Otherwise I'll wait for the day I get Gwenpool