In general, the common consensus would be to build for positional defense rather than mez protection, since if you arent hit, you arent mezzed. And just carry a few break frees for the rare cases where you are hit through your softcapped positions. The investment in powers and IO slots to achieve even moderate mez protection compared to melee type ATs who have status mag protection built into powersets is kind of prohibitive, if you really want to secure windows of decent protection, use the sorcery pool for rune of protection, but this requires a 3 power choice investment.
Personally, I just build for softcap range positional, then stay out of melee or aoes that might mez me, and on the rare occasion Im hit by something, just pop break frees and continue blasting, making dead the offending mezzer as priority.
Why build for something that you can easily just use a handful of inspirations to avoid? Build to your strengths, which is pumping out more damage and play positionally so you dont get caught in situations where getting mezzed is frequent.