Exposed necessary or optional?

Right, but you need a lot of crit glyphs before that kicks in. It’s not like TSW where you could stack Deadly Aim + Elemental Force and have near 100% crit chance off the bat. It’s under 20% chance with max purple glyphs which iirc is just shy of e6 on an even character, obviously into e6-7 for someone who does less scenarios than dungeon/lairs. At that point OS is worth like, 2.4% dps. There are plenty of actives worth more than 3 times that (for group) and some worth more than 5 times that (dps-only group)