My mastery is ranked 5 and I have Excalibur, Oberon, ASH and Rhino Prime.
ASH is prob the most fun warframe ive played yet. He is awesome at being stealth and hidden. Shade works best with ASH and I use the deadly dread bow, supper charged.
My mods are Serration rank 7, Shred Maxed, Metal Augler Maxed, Cyro Maxed, Speed Trigger Maxed and bow mutation.
I think I put posion on there too I forget lol.
Rhino Prime is badass tank but he does run into trouble with walkers ive notice, and if your not using Rhino skin active they will drain your shields very very fast. With ash ill do a smoke screen for all heavy units which puts them in a daze like Excaliburs just with less smoke, then I go around and chop everything into little chunks. Ooooooo yea. Warframe is my crack!