Finally got my Verus Iron Shield case 

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Haven't checked Note 3 spec. What puzzles most of us is that there are so much space within these massive device to make good antennas but the performance is still poor.

May be they realise that no one can really check antenna performance hence it won't impede their sales. Apple products' antenna was bad, with iP6/6+, it improved by leaps and bounds.
Soft optimization may help but it won't make much difference.
The test methodology is quite complicated and it varies with frequency, primary/secondary antenna and a few more factors. I can't remember the figure on top of my head now.