Pre-MoM
A lot of people balanced between mitigation, health and dmg. (Overall build)
Some people went ahead and played the morale whore and died to quick because of low
mitigation, also didn't have enough DPS. (Health Build)
Then there was the DPS build. Full DPS corruptions as well as either 1 health or 1 mitigation. Not many Reavers played this Pre-MoM since they were greedy and figured the longer you last - Health Build - the more inf you get. Not really the case, your DPS is outrageous and I currently use this on my Warg Post-MoM. (Damage Build)
Post-MoM Pre-Book 7
Imo, there was really only one build you could do Post-MoM Pre-Book 7.
That was going for full DPS, Post-MoM was all about killing that Freep no matter if you charge into EC and die. You get that Freep dead! Health didn't really matter, If you were on the Freep's RAT or their main target 90% of the time you will be dead 4.5k morale, 7k morale It made no difference at all.
Post-Book 7
I've only played it for 2 days so I can't say much, but from what I see is you can now balance between Health and DMG. Mitigations are nerfed so they aren't as useful as they were Pre-MoM.
Hope I could help!