It helps them, but it's not a Defender fix.
It does add 6 green moves to their dial, which means they get more from the upgrade than every other TIE ship.
It gives the Defender more options when stressed, both with self stress abilities (opportunist, push the limit) and with enemy stress mechanics (Rebel captive, tactician, R3-A2). So yes, for 1 point you have a decent chance of pointing the right way, something you didn't have with the Defender before.
The other thing is, Defenders didn't really have a lot of good options for modification slots anyway. Engine Upgrade is expensive on an already expensive ship, and gets the most out of PtL and Barrel Roll, which as we've already decided, I think is bad for a Defender.
Hull and Shield upgrade increase durability by roughly one sixth, for less than a sixth in points, which is not bad.
Stealth Device I've seen a few times, but never run myself, as I think it's best if you can focus/evade in the same turn.
Nothing else really benefits the Defender, so yes, I think the 1 point TIE Mk2 is a much better buy than the 3/4 point Hull/Shield/Stealth.
Again, not a fix, and certainly not something that will make Defenders competitive. But for those of us who love the ship and fly it anyway, this is a very good upgrade that gives the Defender more options.
Edited by Rividius