My guild 4 manned HM EV back in 1.2, I wasn't there for that run though so I don't have much to add.
I was in our 6 man of NM KP back in 1.3. We had the same maintank from the HM EV run and he told me that 6 manning NM KP was harder than 4 manning HM EV, so once you've 4 manned HM EV (congrat's on your 5 man btw
) you might want to try your hand at 6 manning NM KP.
Sadly, back in 1.3 you still got BH comms from doing NM KP and so there was an incentive to low man it if less than 8 people showed up for Ops. I guess we could try 7 manning HM EC sometime, but I'd rather focus on clearing NM EC (NM Firebrand & Stormcaller are ******).