No, they didn't remove diminishing returns, but charge/intercept are seperate from the mace stun proc, and then the TuF/earthshaker procs are seperate from that. But I've been in fights where I get stunned 4 times or whateven then I start seeing IMMUNES pop up in my SCT.
Fights are basically...
Charge stun, mortal strike, auto attack, mace stun, whirlwind, mace stun, auto attack, TuF proc, auto attack, mortal strike, mace stun.
Its fucking stupid.