I'm like 99% sure the balance team wasn't able to animate the parachuting in due to game engine limitations so they had to settle for infiltration. The first iteration of them had them appearing inside a smoke barrage like god damn ninjas in lieu of parachuting but you can imagine why they scraped that lol. I think the 3X DPs are fine - they do more damage than Regular guards and can be fired on the move which is a big perk. I think the most they need is a better/reworked Vet 1 ability and maybe give them Suppressing Fire similar to Paratroopers' ability (or have that be the new Vet 1).
I think swapping the AT strafe and the pinning strafe is the way to go. It's easier to swallow an AT strafe beating your tits in if it needs a Vetted unit in range than a global off map. Plus AB guards hit Hard enough that an AI strafe is a bit redundant.