About group teleport - rather than teleport yourself and then recall friend each of your teammates (if they survive), it's like teleporting everyone for 1/3 the distance of regular teleport.
It basically cuts out the waiting/interrupt time for recall friend. I'm not sure if it still stuns your teammates after you use it, though. I don't think it's very useful since I personally use recall/teleport combo since I usually only duo.
As for being hit while you're teleporting, yes, if someone fires a shot at you before you teleport it will follow you and have a chance to hit you after you teleport. The upshot is that it will take longer for the shot to land and I 'think' that the damage is not subtracted until the animation hits you, thus allowing you to regen more life...kinda hard to test. It's the same with any other travel power except teleport is the fastest way to get out of range, assuming you have enough endurance and skill at using teleport to maneuver indoors, since you don't 'exist' in the distance in between teleports.