My guild jumped straight into heroic, got 6 bosses down in 4 hours.
Skorpyron was a one shot.
Anomaly was a one shot.
Trilliax was 2 pulls.
Spellblade was 3 pulls.
Krosus was 4 or 5 pull.
Tichondrius took the rest of the night, around 8 or 9 pulls if I recall, but we did get him down.
It feels like there's a pretty steady increase in difficulty. If the last 4 get harder at the same rate as the first 6, then I think with Vantus runes we might get Elisande down this week, but we will not get Gul'dan on heroic.
So far, the raid is really fun, loving the shit out of it. Tichondrius is healing intense as fuck though.
For reference, my guild was 7/7m and 2/3m before NH came out.