I hit several Dollar Trees today hunting for DVDs/Blurays and noticed some local trends involving "Final Faction":
The least popular human figure in my area is Shift. Many DTs have nothing but her left from the heroes.
The least popular hero accessory set in my area is the Aerial Assault. It was the only hero set at any of my local DTs.
The Kharn seem to sit longer than the heroes in my area (when restocked at the same time), same for their accessory sets. I guess kids want the soldiers more than the monsters here.
The figures (both factions) seem to move quicker than the accessory sets. A few DTs have nothing but accessory sets (mostly Kharn) on the pegs.
Your experiences may vary, but this is what I am seeing in northeast NJ.