Numbers here are what I used to get on PLD, before I got Justice. Can't remember my normal TP return since Justice. It's probably 13, but since I haven't been paying enough attention to it, I'll just use my old numbers since I know they're correct.
Main Joy (6.1 TP/hit, standard Vorpal return of 9): 4 hits, main 6.1 + 3 for 1 each = 9.1 return
Comp/Joy (normal 11/round, standard Vorpal return of 14): 5 hits, main+off 11 + 3 for 1 each = 14
One issue you run into is that if you do the math, my swords were giving me 5.3 TP each as well, which should only come to 10.3+(3*1)=13.3, but my consistent TP return was 14, without any form of Store TP or Double Attack. The only way to explain that is either that both hits in the Main+Sub round come in addition to the standard 4 hits from Vorpal, or that TP is counted differently when starting from zero. Considering I've never gotten just 10 TP from my first attack round with Comp/Joy, I'd say it's the latter.