This may work out ok. On the surface it sounds like it's going to slow down combat, but after looking over some of the WS data it may end up being the same.

1000 TP WS typically have a 10-20s CD
1500 TP WS typically have a 20-30s CD
2000+ TP WS typically have a 60-80s CD

Let's say they lower the TP per hit from 500 to 300. It would take 30 seconds of uninterrupted auto-attacks at an attack delay of 3s to build up enough TP to get to 3000 TP, however, all the high TP moves chain off of a 1500 TP WS. So the way I see things working from a DPS standpoint, you get 1500 TP, do your high damage chain, get 1000 or 1500 TP, do those chain combos until your high cooldown skills are about to refresh, and rinse and repeat.