I don't think they should get rid of set bonuses but I do think they should revisit non-tier set bonuses. If there were a few gear sets with minor bonuses I think it would make gearing more interesting. Like a set that was a pair of rings and a neck, or just rings, or any combination really. There were a bunch of sets back in classic and some of them were really cool, some were just goofy but that isn't a bad thing. If they made gear sets that had niche uses, like defense bonus or a small heal, a short dps boost. I'm thinking along the lines of how trinkets have been recently. Tanks especially have to collect several trinkets for different fights and I think this sort of thing could be applied to non-tier set bonuses.
As for the tier set bonuses maybe make it so that if you have your 2 set or 4 set you get a visual indication, like your armor gives off an aura, maybe holy pallies can glow and locks will be shrouded in darkness or leave fire foot prints. That would make the bonuses more interesting, but I guess it would be hard to make new indicators for each tier. I don't, i think it'd be cool.