So, I can confirm the following..er..defects:
- The Tyranid AI definitely doesn't like building things so it doesn't go anywhere with just genestealers and spores. It's not my mod and it happens on all strategies. AI is set to Hard, Standard resources.
- The Retributor squad Multi-melta upgrades don't change the unit's model and I'm not sure it does anything. In fact, I have a hard time imagining why I want Retributors over Celestians. They have marginally more HP, and although they're cheaper they cost 3 pop vs the Celestian's 2, and you have to equip retributors (unlike Devastators and Havocs that come with heavy bolters from the get-go). I think it would be best to leave Retributors as T2 heavy inf and Celestians as T3 elite inf. The only problem is faith generation, as Celestians are usually a forces' main faith source along with the Cannoness and Superiors (I don't think anyone builds Seraphims usually). I saw RT2 make models for several extra weapon upgrades for sisters and Celestians. You could at least give Retributors Storm Bolters or Heavy Flamers upgrades (although those are technically Dominions and not Retributors) so they can start with HB.
- Sororitas Sentinels are really fun to field.