I'd argue that Flak Vest/Jonin is more viable than 4th Hokage Minato, simply because of his utility. But I will say Hokage Minato got a bit buffed to help compete with Flak Vest Minato. For instance I found out that when 4th Hokage Minato uses his mystery on a person already tagged, the entire lineup receives tags (which isn't anything new) but I believe he also interrupts the entire lineup if he's able to do this. I experienced this with running a team yesterday in arena, where the opponents Fu had a tag, I capatlized on this to target her with 4th Hokage Minato's mystery, the opponents LM had their Chidori Blade - Shadow qued up as well and Minato interrupted his mystery even though he wasn't the one being targeted. I'd also like to point out they fixed Hokage Minato's text for his dodge, it now properly states that he can avoid mysteries just like Flak vest.