The balance issue, for me at least, was not that we had access to the full range of mods, frames, weapons, and abilities. It was that you spawn in at rank 0 with your mods and abilities mostly disabled.
You gained ranks and gained access to your stuff as you killed, not unlike a moba. Like a moba, this allowed teams to get a few extra kills by taking out freshly joined players and then absolutely steamroll for the rest of the match.
My last Dark Sector match included a few people loading in mid match, myself included, and being able to do roughly 45 damage with a forma'd Dread. Then we