This was basically my experience with Crota.
I did three Crota kills this week. One I lucked out and had this super expert level 32 run the sword. We took Crota out on the first try in two sword holds. The Crota kill took 10 hours, four or five group, and a lot of disappointment.
The first PUG group (for the second attempt) I ran through to Crota and then did a few runs through with them. I knew right away that it probably wouldn't go well based on the experience on multiple wipes on the thralls and a wipe after forming the bridge and multiple players screaming at a Joey to make a run for the bridge and stop shooting. I figured whatever, I'll give him the benefit of doubt and just assume hes never done the raid before. I'm in no rush anyway, so I can take a bit of time to teach the fights and half-assedly sherpa. It only got worse from there when multiple players would not listen to strategy on the death singer stage. No Joey, do not follow him into the room to draw out the witch. No, Joey2, don't run up and shotgun the yellow bar knights. After 5 wipes at Crota and no progress as a team, I left that group. The second group was cool and was stuck at the bridge. Ran the bridge legit until it glitched and the last ogre was at a sliver of death and did not want to die despite 7 gjallarhorn rockets. Wiped and cheesed the shit out of the bridge. We did a few wipes on Crota, got the timing down better (brought Crota down to a quarter), but it was getting late so some of them had to go. Third team (6 31s) had some asshole that kept putting everyone down. Sucked with the sword and probably life in general. After a bunch of wipes, we all just left him alone in the party and in the crystal room. Fourth team had never gotten Crota down twice on a single sword carry.
The last Crota kill, I pulled some people from VoG hardmode run. I think this it where the problem with Destiny's equipment/leveling/RNG system became evident for me.
We had this really bad player on our team. He didn't seem like he knew what he was doing. Before we did a stage, one member would clearly explain the strategy for the stage to make sure that we were all on the same page. The methods were pretty standard, run into the spirit bloom room at legions, don't walk into the green puddles, take one side and stick with it. But Joey decided that he was going to stay alone outside during legions.
TLW; did three Crota kills this week, shortest attempt took about 4 minutes, longest was 10 hours.