We did several little tests last night with a friend. I have some remarks. Being high, behind a cover is just too powerful. We only get hit on 6+ and block on 3+. Conversely, we respond to 3+! In each of the games, the tall characters completely unbalanced the game.
Another problem is the number. We chose to test two completely different bands. One of 10 miniatures with just one weapon and the other of 5 miniatures + armor + piercing ammunition. With 5 activations you end up being completely overwhelmed and the opponent can simply use 5 or 6 activations to go around the table with a figurine and arrive in the back of everyone and make a box with the last 4. So being more is too advantageous.
The game system is really nice, but we felt that something was missing to better balance the game.
Regarding the second point (model count) - this is one of the major considerations in infinity - list building requires a balance of enough orders and enough quality models.
There is skill to limit and defend boardspace through reactions. Admittedly, in infinity, there are more options to have stronger reactions. But a low-model count double-tap list should have models with high quality reactions on models that are harder to take out - and thus consume more orders to deal with.
My point is that trying to hard to balance this with rules / points may detract from the tactical proceses of double tap