R4 5* Starky, Nebula, or Sentinel

Boomhauer_1

I use Starky in AQ map 5 (with 4* Blade and GR), Nebula in AW (with 5* PM and 4* Corvus, and I want to use Sentinel for the harder content (100% Act 5, 100% uncollected EQ, etc)

Octoberstack

Sparky can more than hold his own in Map 5 at R3, whereas a R4 sentinel will give you a significantly easier time in Act 5 as well as V2 and especially V3. He's still very effective in said content as an R3, but the increased damage output as an R4 will leave less room for errors in lengthier fights, and the increased armour/healthpool will mean you can afford more mistakes.