Modan Spellbreaker Agency is dwarf centric (not exclusive). [A-RP] Modan Spellbreak Agency -- Heavy Dwarf RP, DF Expac! - #9 by Dwoln-moon-guard
Depths of Shadowforge is another Dark Iron focused guild (not exclusive to dwarves). A-RP [Depths of Shadowforge] - Shadowforge/Dark Iron RP Guild - #7 by Torchforge-moon-guard
There’s also the dwarf political rp community, Assembly of Three Hammers [A-RP] The Assembly of Three Hammers (Dwarven Senate)