I have thought about this for a while, but decided (pretty late I know) to mention it.
1. Season 7 Rep System change is designed to make set gear more attainable and more consistently attainable. There are going to be a lot of people waiting on one lucky drop to have a full MK XII set of some sort. They understandably feel pretty bummed that for THEM the chance maybe went down to finish the set sooner rather than later.
2. People want the sets complete for the set bonus. Many are stuck currently in the terrible loop of running a certain instance to death to get it. Agreed this system is terrible. Rep system, once caught up for current STF veterans and elites will be a HUGE improvement.
3. Set bonus is the same for all sets, (MK X, MK XI, MK XII) only the base values of each individual piece change.
4. People may not have been thinking in terms of using EDCs to finish out a MK XI set while they wait for the final piece (likely the engine for space and the psg for ground) They may be running the soon to be nerfed 3 piece borg plus whatever shield, since that's better than full MK XI.
SUGGESTION: Omega/Honor Guard/M.A.C.O./Borg/Breen/Jem'Hadar and all other sets should unlock the bonuses regardless of Mark.
RATIONALE: If someone is in the terrible spot of needing one piece to complete a set bonus, they are gonna be in for a really long wait to finish the set. I myself am running CSE over and over since the only thing I could want from the current system is MACO Engine. (Have full MK XII Omega and two of three MACO) With this change once the MK X gear unlocks there will be a really nice reward. The incentive would still be there to grind up to get MK XII, but at least that player can now PvP and do other EndGame non-STF content that really demands sets to do well.
So in other words, MK XII Shield, MK XI Engine, MK X Deflector = 3 piece bonus. Overall stats not as good as full MK XII bvut very serviceable for EndGame while working on upgrades.