On my system, using the C-130H Japan AF, I'm getting 38 FPS (external view). This is at YMML and my add-on scenery is as follows:
Orbx FTX AU Australia SP3, Orbx AU YMML v2.0 (Melbourne International), Orbx AU YMAV (Avalon) and REX2. I don't think I would call it a bug.

What a your system specs? If you provide those, then we might be able to see why you are getting such low frame rates.

Mark