Ability damage bonus from upgrading armor not working?

Playing as rogue, Jumper Deft Leathers give +30% Ability damage.

After upgrading them by buying an additional set, and getting them to +2 (as Uncommon), this is increased to +45%.

But, ability tooltip does not show difference in damage dealt before or after. I even tested it in combat against the same enemy and both cases deals same damage, as if extra +15% does not exist.

Note that stats window correctly shows that ability damage got increased (from +86% to +101% bonus).

I also did additional test with Worn Leathers, by upgrading them at Lighthouse to +2, and same issue happens. The extra +8% you get from that upgrade does not seem to be applied.