If you're looking to spend Ironite on Sands of War refils for the Arena or Gauntlet, I think you're better off spending the Ironite on Sands of Time refills to farm the Trooper dungeon.

I did a mini experiment by opening the Trooper dungeon, spending 90 Ironite on SOT refills, and sending off an autofarm team. I ended up with 45 SOW instead of 30 after 30 runs in about 45 minutes.

I also got 20 Ironite back, 100K gold, 30K XP for my toons, 30 runs credited towards achievements, plus a couple talismans, some XP runes, and some Warrior fragments.

It's a small sample size, but I'll definitely be doing that more going forward.