There are quite a few times you can use Shadow Claw. You mention a base power of 70. Night Slash has a base power of 70. Fire Punch, Thunder punch, and Ice Punch only have base powers of 75 and yet they are fairly common.
Shadow Claw can be used on Zekrom for coverage, when the battler doesn't want to be locked into Outrage. Can also be used on Blaziken to take down Giratina and Arceus-Ghost. BandFerro uses Shadow Claw. There are several options in which to use Shadow Claw, although you will sometimes find that there is a preferred move for coverage or to take advantage of STAB or a particular stat.