Does the stats on Bungie.net tell you what difficulty you were playing on?What you described sounds like normal Crota. If your PSNID is what you put in your B3D profile, it looks like you cleared normal too.
very little people allow 31s to hard mode let alone 30s. If your warlock can 2 sword crota, either he will have to 3 kneel him every time, or he has absolute perfect timing (R1R1R2R1R1R2R2 combo), both of which I have tried (and proven that they're doable) and can say is quite difficult to do. (but very easy in normal mode)
That's with 7 HM clears under my belt now.
And I did play on hard, though the guys I was playing with they had perfect co ordination, infact it was quite amazing to see them play together. Being lower leveled, I was more on a ride lol. This is the first time I've managed to beat Crota with my PSN id, the only other times I did was two other raids with a friend's PSN id but on normal.