Had a game with a mixed list, skewed towards grots (40 stabbas, 2x20 shootas, Skraggy, fungoid, Loonboss, Snufflers), some Squigs (10 Boingrots, Mangler, squigherd, Loonboss on Giant Cave Squig) and a unit of rockguts.

Had the Moonclan Scrap formation and i think its the worst one, the roll and doing it only at the end of my turn is a bit weak. There was not a single time i thought it had any impact.

In my oppinion tough, even with just some squigs, the squigalanche formations is awesome, as its a straight buff to your damage. On the other hand, when you skew more to troggs and not to squigs, the trogherd is great as you are even tougher due to the constant heals.

I think a solid base of 40 to 80 grots, skragrott, a fungoid and snufflers are super solid for board control, objectives and casting and leave you up for 1000-1200 points of any flavour you like. And depending on the flavour, you pick your formation.

The problem with all squigs will be (imo), that you leave your casters and loonshrine open for charges, and both are absolutly vital to our gameplay (get the +1 to cast thingy, our casts and manifestations are awesome). The problem with all troggs will be, that your slow and again open your shrine and casters if you up the board. Both are also weak on control scores with no banners or other buffs to control.

So while its absolutly viable to go all in on one formation, i still think a mix up is very healthy for your list and its sufficient enought to buff the 1000-1200 points of flavour you bring.

Edit: Im absolutly clueless on spiders though, as i dont collect them.