You may be biting off more than you can chew if you're running at party size of three while solo at level 23.
Compared to Invulnerability, which I have recently started a character with and who hit level 23 at some point this past weekend, while you have increased regen and some To-Hit debuff, your underlying resistances from the set are about two-thirds that of Invulnerability (which does not have the regen or To-Hit debuff). At 23, fighting yellows and whites with no additional adds, a pack of 3 would leave him sufficiently down in health that I would only subsequently engage another pack of three before taking short, kneeling health/endurance break. By contrast it seems you are running into spawns with 2 additional foes--fighting five at a time.
Bear in mind that while To-Hit debuff helps, the value you are getting from Rise to the Challenge (according to Mid's) is -3.75%. Even slotted it will end up at just under -6%. So instead of a 50% chance of being hit your foes are hitting at 44% (i.e., you've reduced incoming damage on average by about 10%). You do not mention if you've slotted in damage resistance enhancers yet. If not, try putting some in Mind Over Body (first) and High Pain Tolerance. Also, grab Tough from the fighting pool (on your way to Weave).