DH has a Specialized hybrid and he loves it. As far as fit goes, you have a little more room for adjustment on a hybrid than on a road bike. DH's has an adjustable stem, but the only way to move it closer is to also move it up, so I would make sure your reach is at least close to correct. Lots of hybrids have geometry a little like a compact road bike, so that should give you more seat post to attach the trailer to, as well as plenty of standover height.
I would guess the reason your knees felt high was because the seat was too low. My observation at the bike shop is that when anyone test rides a hybrid, the staff sets the seat too low on purpose. Most people are worried about being able to touch their feet to the ground while still on the seat. Considering the larger tires raise you off the ground even more than on a road bike, I can't imagine you could have the seat at the proper height and also be able to reach the ground from the saddle. Get them to raise the seat to the proper height for a test ride and see how it feels.
Most hybrids I've seen have front suspension. I think Raleigh's lowest end hybrid might not, but I'm not sure. Fuji makes some flat bar road bikes that you might want to consider - they seem to be halfway between the hybrids and a regular road bike. Hybrids are really fun bikes to ride, in my opinion, though. Good luck finding one that meets your needs.