The Hive Guard would bemore of a Blitz guard while the Pyrovore is more of a front line creature. If used in Wh40k they are commonly dropped from orbit.

_________________
We are returned!
http://www.epic-wargaming.de/

I really don't think Hive guard should be units on the epic battlefield, just shooting attacks on fixed structures.

_________________
http://www.troublemakergames.co.uk/
Epic: Hive Development Thread

And I fully expect that to be a commonly used with whatever fixed structures are in lists. However the background clearly states that Hive Guard do appear on the front lines as a counter to mechanised enemies, the Hive Mind can suppress the protective instincts and drive them forward. Therefore it should at least be a unit option even if the initial lists don't use them.

I'd suggest a compromise: Hive Guard as a Unit, but only purchasable by formations that have a Nest as their synapse creature.

_________________
Currently doing a plastic scenery kickstarter

Something like that. They won't initially be in my new-stuff list, but can either be added at a later date or go in other varients.

_________________
http://www.troublemakergames.co.uk/
Epic: Hive Development Thread

I wouldn't even go that far. A brood nest should have the Hive Guard abstracted into its weapons and stats (like in Leviathan). Then there should be a Hive Guard unit as discussed here. The list decides on which to use if any. The lists themselves can deal with any special buying clauses if they are required for theming.