As someone who took Durable for their character, I think its fine. Its a bit niche, but it does exactly what it says its supposed to do, make your character feel a bit more durable.
I'm running a human Eldritch Knight, and I took it at level 1 for my variant human feat.
I had an odd valued score for con (13), and a con score generally lower than I wanted (since I put my best stats in STR and INT).
I'm currently lvl 9, with 7 levels of Ftr (EK) and 2 levels of Wiz. My con bonus is now +4, so the 8 point min healing when I spend my wizard hit die during a short rest isn't a bad deal at all.
Our party just lost our cleric to a beholder's disentigrate beam, so healing between fights really is a concern, and has been on and off throughout the campaign (depending on who is available to game).
Overall I'd say Durable is a balanced feat. It has its uses, some other feats might be better for some character builds, and ability score increases might be better in others. In my case, there were some other feats that I'd liked to have taken instead at lvl 1, but i REALLY wanted to push my con up higher and felt that it was the best selection for me to push up con and help compensate for our limited healing availability. Compelling reasons for me to take it at the time.