Vizunah Square bugged?

Just make sure that you stay with both NPC's til they both start to move. If you get too far ahead, they will be "stuck". Happens in all missions where you have to stay with an NPC. its just how the game mechanics work. The NPC is waiting on you, in a manner of speaking, even if you get too far ahead.

Well that's really crappy because in Vizunah Square it's all about speed. If a NPC slows me down, how am I ever going to get the bonus?

yes after clearing each major battle area try to hang back and have togo and/or menhlo in your aggro bubble until they start their dialog and start moving.

very old bug which as you mention is in a timed mission so its very annoying and frustrating when they refuse to move up.

MOVE IT Togo!!!
/fistshake

If you're clearing the mobs at a reasonable pace then you'll manage the bonuses in time even with waiting on the NPCs

Mhenlo in particular will stop to heal minions, and cease to move immediately after. As such, don't bring an MM if you feel comfortable without one.

Occasionally, talking to them and then waiting just within aggro range gets them moving again.

I've done this many times and from my experience there's many bugs in this mission. Sometimes Togo or Mehenlo will get bugged/stuck right at the end after the 3rd main fight which is lame because pretty much done with the mission and have to restart. A lot of times I've noticed if you're playing with just henchmen on the other side they'd bug a lot also. Sometimes they don't even get down to the main fight area. Last time I tried to do it they started to flee back up the stairs to the start after killing the first mob group. Had to do the mission with just one team, which is not spiffy.

another nasty thing is that villagers all of a sudden transform nto afflicted sometimes, sometimes afflicted 'pop up' as it were. Keeping an eye on those helps because togo and mhenlo will stop to fight those newly popped up afflicted, and therefore fall behind.