Is it common to have substantially different block times on the same route when the aircraft is the same as well?

I am looking at the EWR-YHZ-EWR route, operated with Expressjet's Embraer 145. Most days, there are two rotations.

EWR-YHZ flights always have a block time of 1:57h.
YHZ-EWR flights have either 2:07h (morning) or 2:33h (afternoon). Weekend or weekday, doesn't matter.

As you can see, the block time of the afternoon YHZ-EWR flight is about 1/3 longer than any EWR-YHZ flight. And that is not due to jetstream effect, as the morning flight is much faster. Yes, variations in traffic affect travel time, but wouldn't that be more a problem in the morning rush than in the afternoon, and wouldn't such variations affect both directions?

Generally, I wouldn't care about the block time. I have flown this route many times. But with the current time table, the longer afternoon block time pushes me out of the minimum connection time at EWR.