Bosses, dungeons and events can’t be completed because they become invulnerable or the bar quits moving. My mythic uniques aren’t getting the 5% bonus per masterworking increase. It’s a GA core skill heir of perdition that is still at +4 after 12/12 masterworking where it should be +6 by now. The seasonal reward system is trash as well as the rewards. If this is expected to continue the next DLC’s had better be free.
If you didn’t hit it with any masterwork upgrades, then +4 is correct. It only upgrades the base value, which means it gained a total of 1.2 and then then the fraction rounded down.