For that set up with anything over a 27" shaft/ 100gr head, Easton recommends a 340 Axis .
A 28-29" 400 shaft is definitely underspined.

I was prepared to order some for my BowTech Liberty at 30"/70# and with a 28.5" shaft and 100gr heads, I was definitely going with 340's........The Legacy is a bit faster than the Liberty.
I decided against Axis altogether and went with A/C/C's again myself, but the 400's would have been the wrong shaft for my set-up.