The 15-85 is a fantastic lens for APS-C cameras. It's sharp, and the 15 end gets used very frequently (my Sigma 10-20 gets left in a drawer since I bought the 15-85). 24 is too long for a general purpose lens for an APS-C camera. If you want telephoto, you can pair it with 55-250, which is cheap and outstanding value for money or the 70-200 f/4 L IS which is so, so sharp.
5D IV, 5DS R, 7D II, EOS-M, Powershot G3 X, 400mm DO II, 300/2.8 II, 1.4xTC III, 2xTC III, EF 1.8 STM, EF 70-200/4 IS, EF 24-105, 15-85, 100-400 II, Sigma 10-20, Sigma 150-600mm C, EOS-M5 15-45, f/2 22, 11-22, Samyang 8mm f/2.8 fisheye