How useful are miniatures in the normal ACKS combat system? How many of you use minis to play? I’m considering getting a few fantasy minis and a battlemat but I’m not sure they’re necessary for a good ACKS experience.
Also, what scale of minis does Domains at War use? 15mm? 28mm?
That’s a good question , I recently temporarily lost my mind and spent 200$ on the reaper kickstarter and I’m looking forward to use them.
Warder
You are not alone with that Blackwarder… 
I think miniatures are not necessary for combat though they can help to visualise the situation at hand.
I certainly will use some reaper minis for that once they arrive.
You can play ACKS with miniatures if you'd like. The 5' engagement rules lend themselves nicely to a map gridded in 5' squares. You can also just use miniatures to approximate the battle situation, which is largely how I do it.
Domains at War can be used with any scale of miniatures. It's hex-based, so you simply need to use a hex map that's large enough to hold whatever you decide to use to represent 1 unit of troops. To date, we have played DAW with one of two scales:
For folks who are reallly into the wargame side of things, I suggest option #2 as the "recommended" scale for DAW. Battlelore maps are pretty widely available (either from the boardgames or from expansion packs that sell for about $10) and the 40mm x 20mm basing is used in DBA, DBM, WRG, Armati, and more.