The opportunity cost of shield bash is too darned high

[Tyrial]

I've actually had ifrit go immune on stuns before he starts doing plumes. ...is that a dps problem?

No, it means either somebody else is stunning or you got a retarded Ifrit. That is assuming your DPS is doing average or better damage.

I've had Ifrits that resisted the very first stun and some that didn't resist at all even when there were Derpasauruses in the group that thought it was a great idea to spam their stun skills as soon as the CD was up.