We had a 2010 Jayco Seneca. Loved it. Towed our Jeep liberty without issues for 20,000 miles. Up to Eisenhower Tunnel and Vail Pass we definitely slowed down, but not as slow as the trucks.
I suggest you go to the Jayco owners forum on iRV2. Lots of Seneca owners there. We looked hard at these (I loved them). GVW is 28,000#. GCVW is 33,000#. Tow rating is 10,000#. As long as you underload the Seneca you can easily tow up to a big SUV or pickup. How well, I can't answer. But if you are from those few states which require a Class B or A license to operate a GVW>26,000#, check that out.
I have a 2008 Seneca which is on a chevy with Duramax diesel and I tow a 2015 Jeep Grand Cherokee with no problems. So I would think the new Senecas should be able to do the same.
Here's the situation. We bought a jamboree 30U,gas, and it is awful in the towing area. We talked to a sales person on the Seneca and he said the Seneca would be only about 25 percent better in the towing area. We don't know anyone that has one to ask or talk to about the engine, towing, and if it has enough torque to tow and get up and down hills, mountains without running it guts out. It other words get out of its own way, as well as tow a jeep. Thanks