The 251 will kill panzers and T34s with rockets IIRC. I've never gotten the tiger to die, not even offline (tho I didn't persist more than a couple dozen rockets). You can easily kill the soft GVs.. Jeeps, M3s, M16s. M8s I've never tried.. Or I might have (faint memory of it) but in any case, given that T34s are doable, so should M8s.
And planes are a piece of cake if you're ranged. The time it takes them to start their engines is the same as a 251 rocket's time of flight.