If the Grots were all bunched up.....which you would avoid seeing a Heavy Flamer coming their way.
Fed up for Scalpers? https://www.facebook.com/groups/1710575492567307/?ref=bookmarks
Man I miss mycetic spores. I only got to try this once before they were written out of the codex, but I shoved a brood of pyrovores into a spore and dropped them onto a unit of ork lootas. Orks really hate flamer templates. They nearly wiped out the squad. it was great. Did they survive the next round of shooting? No but that was one round that those lootas were not shooting at anything else.
Does this help current game play? Well a little bit. With the warlord trait that allows infiltration, you can put these guys closer to their effective range. Even without it they make an effective distraction. Any horde army is going to have to deal with them before they get close, so use that to your own advantage. Make sure they are the ones taking fire, and use your ranged bugs to put the hurt on your foes. Buff them with your psykers to up their survivability and you'll hopefully get a couple rounds keeping the heat off your more important units.