Or, you can think of it like this.
Tanks will specialize in VIT starting from 3.2, so they'll have bigger HP pools, allowing them to stay longer out of tank stance (Since they're also making adjustement to make stance dancing smoother for all tanks), avoiding the damage penalty, and thus doing more (and more consistent) DPS than current STR tanks.

The new damage formula will bring lower numbers, but the context will surely even it out.