I have had great luck with Sigma. I had a fantastic copy of the Sigma 30 with the same bad reputation that I sold when I got a 5D. I have since sold the 5D and repurchased the sigma 30 again and this copy is just as good. I have had seven Sigma lenses and the only less then stellar one I have had was the non macro 24-70 f2.8 that was soft at 2.8 but focus was fine. I am prepared to take my chances and if I have to send it to sigma no big deal.
5DIV, Elan 7n, 400 f4 DO I, 100-400mm II, 1.4x TCIII, Tokina 16-28 F2.8, Tokina 12-28 f4, 85 f1.8, 50 f1.8 STM, Flashpoint 620m, YN14EX.
A7rIII, A6300, 100-400 GM, 85 f1.4 GM, 90 Macro, 55 f1.8, 16-35 F4, 35 f2.8, Batis 25 f2, Samyang 14 f2.8 AF, MC-11.
D500, 200-500, Tokina 300 f2.8, 35 f1.8
S110, D20, Hero 6, 3+