No, factory overclocking shouldn't do that. I have a 2070 Super Overclocked, comparable to a 1080ti, and I have yet to exceed 75°C.
A Tom's Hardware review
here for the ASROCK Phantom Gaming X RX580 8G OC shows closed case temperatures peak at 80°C under load and 81.2° under stress (Furmark Torture loop). The cooler works as it should which is good, but temps are still on the higher end and the clock takes a hit.
Looking around a bit the MSI Radeon RX 580 Armour 8G OC also appears to run hot, so temps are likely similar to the ASROCK in case. The linked article doesn't say which case was used, but I'm certain they used a properly ventilated case, so your 85°C could be case related since 80°C appears to be the AAA gaming temp for a RC580 OC card.
*I couldn't find much on the MSI card beyond thread discussions. You may find something that I have not.
85°C won't hurt the card, but you won't be getting the most out of your card and I'm sure the fans are loud.