Looking over one of the character sheets for a 7 Rogue / 1 Monk.
HP 43, AC 18, DPR 29, AB 8
Evasion is kind of like Avoidance (going off of memory here), so the effective AC is 19.
Defensive CR starts at 1/4 and adjusts 3 steps to 2.
Offensive CR starts at 5 and adjusts 1 step to 6.
Average CR is 4.
This seems about right. The rogue would need an ally to maintain sneak attack damage for each round. I could see a level 4 party taking the rogue to task without too much difficulty. While the rogue could hit hard, a level 4 or 5 party could gang up and take it down in a round or two.