Sudden shift lets you teleport up to 10ft to a space you can see, so RAW you can't teleport behind an enemy, but i'm wondering if that's always the case.
Let's say i'm against a regular, M sized humanoid in position A while i'm in B:
O O O
O A O
O B O
Am i not able to see the floor behind him? Is it impossible for me to see any of the 3 squares behind him?
What i'm interested in is getting behind enemy lines / joining an ally / flanking with an ally that's next to me...etc.
If i can get behind an enemy with one teleport instead of two it makes the ability much better
Oh, that should work fine then IMO. A Medium humanoid may be moving around in its entire space, but it clearly doesn't occupy the whole 5'x5' at once. That's why creatures only provide soft cover, not total cover like a block of stone there would.