Absolutely love these bugs! And they’re the new hotness since the BOB and chapter approved books.
I have two and I normally end up running both (Unless I’m going full kraken). I’ve been giving both the 5++ count as double wounds for degradation chart adaptation. They’re biggest flaw is they’re durability. They need babysitting with a malanthrope for synapse and the -1 to hit.
I used to run them Jormangandr for the 2+ save (fantastic counter against Deathwatch who wound these guys on 2’s with storm bolters) but since the new Kronos spell, they’re a mainstay in a Kronos detachment now. The in built +1 to hit makes the spell trigger additional shots on 5’s which really helps pick up the misses.
They’re new strategem is sweet too, because LOS is a problem. So moving and still counting as stationary can really come in clutch.
The adaptation to cause mortal wounds with them is a trap IMO
. They become target priority number one. They can do plenty of damage with the Kronos pell and pathogenic slime strat.
My advice if your running them, give your opponent a more pressing first turn threat. My favourite is the genestealer sling shot. Absolutely has to dealt with or suffer severe losses and leaves Exo to do work.