I played the 6 man HA weekend for endless hours and it does indeed reduce creativity in builds. Logic dictates that there are less possibilities to combine 6 positions into a team than with 8 positions so there is honestly no need to debate this. In practice, in most builds 2 positions will be reserved for monks and at least one for a melee type (Warrior, Thumper, maybe Dervish soon) so that leaves only 3 positions for build variations.
I loved HA because it was the place I could do high end, strategic style PvP. To a guild like mine, GvG is utterly pointless. We can get on the ladder sure, but when we reach a certain rank we ALWAYS will meet guilds we're not able to beat ever. This will never change since we're a PvE/PvP guild and we don't train GvG for 10 hours a day like the top guilds do. We can reach like rank 400 maybe and then we will bounce back.. and forth.. and back... and every 10 weeks our rank will get deleted to emphasize on the pointlessness.
HA was different than that, because on a lucky day we're able to win it. That's the big difference between HA and GvG to a guild like mine. Sure, we still can try winning HA and it might become even easier to win there since most hardcore PvPers will likely avoid it like the plague from now on. But I won't be able to do high end PvP in GW again (at least not in any meaningful manner) and that's what makes me sad today.
I don't mind a 6v6 arena since it's plus is that it's easier to get a team up than with 8 man arenas and it will cater to many people who want something between the boring TA and the strategic GvG combat. I just don't understand why 8 man HA had to die to erect a 6 man arena in its place. HA was the place for "casual but interested" PvP players to do strategic PvP and it's gone now.
*is wondering where to do PvP now*


