I'll start with the type of answer that the OP is looking for, and then I'll argue that you should ignore this answer.
Answer to OP: If you can't manage 1 pt/hr by the end of intern year, you're falling behind. If you can't manage >2 pt/hr by graduation, you're not ready to be an attending.
The real answer: This question comes up over and over again, and each time it demonstrates a fundamental misunderstanding of EM. Now, please don't take offense. This is a misunderstanding that I too had as a resident, and even as a fresh attending - gotta see 2.5 pph! Four hours into my shift I'd tally up my list - 10 patients so far…sweet, I'm right on track! Wrong. Why? Because the XYZ pph assumes that your work flow is consistent. Being able to reliably chug through 2.5 pph isn't what makes a good EM doc. It's far more important to be able to handle the surges. When 6 ambulances arrive within 30 minutes you can't keep up the 2.5pph pace. You need to shift to the 'eyeball 'em & enter orders based on vitals & chief complaint' pace until things slow down.
One of the best EM docs I know looks positively lazy when the room is slow to medium busy. He let's the PA's pick up patients and meanders from room to room, taking time to drink his coffee. But when things get busy the dude looks like Flash Gordon MD and dispositions come astonishingly fast. Compare him to Dr. Pencil Pusher who gets antsy if someone picks up an ankle sprain on his side when it's slow, because he's worried about maintaining his 2.5 pph. After 8 hours, they've both seen 20 patients, but you'd much rather get sign out from Flash Gordon than Pencil Pusher. Why? Because handling the surge has a much greater impact on the ED than maintaining a pace.
So, if you're a senior resident or an attending, how do I think you should be evaluating your pace? Look at two things: How long are your room-to-provider times? How does the waiting room look at the end of your shift? If patients get seen promptly, the waiting room shrinks during your shift, and you average 2.1 pph - please come work for my group. If a lot of your patients wait in rooms for >30 minutes before being seen and the waiting room swells during your shift then I'm not at all impressed that you average 2.6 pph.