I've heard the idea that he could be used as a "silence alternative" on things like Sylvanas etc., but that seems like a really rare scenario, and I can't really imagine tech'ing him in for something like that. There are plenty of things I could use the dust for, but want to make sure I haven't overlooked a reason to keep him (he is a Standard card at least, so he's got that going for him!)
In addition to Sylvanas, transforming a minion clears any death rattle, taunt, or whatever other effect they have as you know... Since it's random, it's hardly reliable. Seems to me like a junk legend that wouldn't be missed.
Tink is probably most useful as an early minion/super chancy polymorph in an all legendary deck. If you plan to run an all legendary deck one day, you may want tink if better early game legends aren't released by the time you could make a good all legend deck. Even considering this outside use, 400 dust is likely worth much more now, than the 1200 dust loss a year, or two years from now.