Some kitchen ingredients better than others for clumping??

This is definitely an AI thing. Most enemies from my recollection take a half second before they decide what to do when Taunted, some even complete whatever attack they were previously going to do first. Kitchen monsters seem to have particular cycles of caution and attack. All of this probably doesn't involve Hydra though (since Taunt isn't particularly consistent at getting large groups of enemies together). I would recommend Stampede, Act 6: Crisis, Death Mark, or certain pet moves. Lullaby and Dance of Death are also useful here, and likewise for Crisis Escape. Rank 1 Raincasting in combination with Crisis Escape means you won't really ever get targeted, which I believe to be the ideal way to do anything in the Kitchen Dungeon. Also note that since most on-summon pet damage will hurt/kill the Kitchen monsters, you can use pets like Bone Dragons to kill far off enemies and summon new ones in the center of the room.

The short of it is: Taunt will get in your way; instead use moves that reduce AI issues like Raincasting.

As an additional note, at higher ranks, Hydra kills quickly enough that if you just get Glewyas to die first via aggro manipulation of the kitchen utensil, you don't even need aggro management tools. Just put the hydra down in the center and the food will die before it can walk out of range - plus with Glewyas dead, the food will naturally aggro onto you.

That's not matching my experience.

Yes; I was encouraging an early death for Glewyas, and was then placing the hydra in the centre of the room. But when food respawns, it respawns already moving, so they can move outside the hydra's radius of damage before the next tick of damage happens. So if I do nothing I usually end up with 2 or 3 mobs outside the damage range when I can only afford to have one out there. This why I'm standing on top of the hydra trying to find ways to attract them back to me.

Am I missing something? I've been back through the cylinder list to see whether I overlooked an upgrade that would increase the hydra radius, but I couldn't see anything.

Also, just noticed the hydra page claims that at level 1 the training counts were 6 awfuls and 7 strongs, so I've updated that to the current requirements of 7 awfuls and 8 strongs. Not sure when that changed, but maybe some of those who posted replies managed to complete Rank 1 when the counts were at the lower level, which would have made it significantly easier.

Thanks for suggestion of Stampede, Act 6 Crisis and Death Mark. While I've now finished the training for my giant, I'll try the latter two for my human and elf.

I'm not following your suggestion re Crisis Escape and Raincast. If I lose agro I'm getting too many mobs wandering outside the damage radius of my hydra, so I'm not progressing the hydra training requirements.

The strategy involves using Raincast, dropping aggro (with Crisis) whenever you might get it (rank 1 Raincast doesn't entirely prevent aggro), and then using Hydra. If enemies walk outside of the circle I kill them with things like on-summon pet damage (for example, bone dragons deal damage to a flight-line when they get summoned that can hit even enemies far from you) and dance of death. Those two examples might kill enemies that are within hydra range, so you might need to micro manage a little. All of these will stun the enemies when they get hit and prevent movement for a second (you can include Shock for stuns that will likely not kill the dungeon monsters).