The question was about K2200 (maxwell gen 1) not K4200 (eg.K4000 described in OLD nvenc SDK pages), but Ok. I did not received any official answer from nvidia (eg. > 2 month).
There is NEW nvidia video codec SDK version 6 and nvidia changes 2+ encoder sessions support - https://developer.nvidia.com/nvidia-video-codec-sdk.
New SDK (by webpage, not verified) supports 2+ encoder sessions on more cards (including >K2000 also maxwell gen 1 K2200) and new maxwells M* too. There is also removed licensing bug if you combine non-low-end and low-end/geforce card in one system (<=2 encoder session enforced on low-end/geforce card only, eg. N (unlimited for non-low-end) + 2 (for all low/geforce) encoder sessions allowed per system). Now I am slightly happier.