I don't believe that Interstate can't make a good 6 volt battery. They are one of the favorites on this forum and others. You can't draw 2 amps from any battery and have it keep a charge for long. It's a LOT more than a "parasitic" drain. Here's what I would do. I would break the problem down and try to find WHERE the drain is happening. You should be able to do this by using an ammeter. First determine with the ammeter what the drain current is. Verify that it is 2 amps. Then, with the ammeter still in the circuit, start pulling fuses one at a time, noting which fuse, when pulled, drops the meter reading significantly. It may be more than one circuit that is draining, so check all the fuses. When you have found the one or two fuses that affect the reading, you will know what appliances are responsible (assuming your fuses are labeled). Any competent tech should be able to do the same thing, but, as you found out, they don't always come up with complete answers. You may also have weak batteries or batteries without enough water in them.
2004 Tiffin Allegro 27.5 ft. P32 18,000 lb GVW. 8.1 liter. Workhorse chassis built May 2002. 24,500 miles. 2012 Jeep Liberty Toad. RVi2 brake unit.