I don't see why it shouldn't count, it's the same fight, you just don't have to convince the whole team to sit around while you do it.
Did you fight regular Romulus or nictus Romulus?
I don't think there's much more value in having to grab 4 fillers and ask a friend to lend you a character just to start the TF. 
That being said, both versions of Rommie are level 51 minimum in the ITF.
So I took down Romulus with Variant, my DM/SR.
I'm thinking that because this was in AE and not the ITF that it shouldn't count towards my AVs killed list.
It's just that AE is such an easy way to get to solo AVs but I'm not sure about that value of it.