Drop rates have been all over the place. I was running 208% luck yesterday before patch, got fuck all from contracts (legendary and normal) all run on GM1, also did a stronghold and got jack and shit. Logged in this morning before patch and did 2 strongholds, first I walked out with 3 MWs, and the second was 2 MWs and a Lego. Switched to all my top level gear which I think has zero +luck on it, and run some more strongholds and got 1 MW a run. Then the patch hit, still in zero luck gear and pulled 1-2 MWs per stronghold after that, I did this about 5 times. Did 3 legendary contracts and got 1-0-1 on those.
Did the standard contracts, first 2 with zero luck, 0 MWs, and bugger all loot in general. Switched to the +luck gear and did the final contract. Had a Legendary drop in the first minute. Saw a bunch more Epics than the other missions.
I realise these are tiny sample sizes but overall, after 70+ hours of gameplay I can't help but think that +luck is the way to go, at least while you're trying to gear up.
Going to try a 100% luck build so I'm not so weak in GM1. It's doable, but it just doesn't have the massive amount of armour and regen that my higher level gear has. I guess I just need to keep farming MWs with +luck on them.