Last Stand uses:
Magmaw Mangles: Last Stand+Enraged Regen makes healing the tank during mangle easymode, and can also help survive that initial DoT tick that hits at the same time as a melee swing.
Maloriak: Uh oh, there are 12 adds up. Last Stand/Enraged Regen/Shield Wall while picking up the final three, then start kiting.
Chimaeron: Double Attacks each hit for 180k. I generally raid at 170k buffed. There are 2 in a row at the beginning. Shield blocking the first and Last Standing the second before the Massacre helps ensure you'll survive that second Double. It can also be very useful in conjunction with Enraged Regen during Feud to lower the healing load.
Halfus: Any time you're taking more damage than usual. Tanking 2 drakes at once, tanking Halfus with Malevolent strike stacks. This can take a bit of the pressure off of the healers.
Double Dragon: Phase transitions when the ranged all have to get stacked, LS+ER can keep you alive while the healers have to run around. Also good for, "ZOMG, all the healers just got hit by the Deep Breath. I have to keep myself alive until they can make their way out of the twilight zone."
That's just in the fights I've done so far. If you have no other use for it, LS+ER just simply takes pressure off of the healers. It's a good cooldown.
Kathy, I said, "I'm lost" though I knew she was sleeping
I'm empty and aching and I don't know why
Counting the cars on the New Jersey Turnpike
They've all gone to look for America