First of all, deception is nerfed so dont except something big but start with this opener.
Always lacarete x 2 then stealth, and cast is crushing darkness (you should start with countdown, not after the fight start). After that recklesness, discharge, Phantom stride,adrenal,discharge,balllighting,maul, volcanic slash x 2, maul,discharge, force cloak,recklesness discharge.
You should be able to cast 4 discharge before the adrenal runs out and it should give you 6.5 - 7.5 k opening dps according to your gear. After that you should be pull around at least 4 - 4.5 dps depending to fight.
As assassins we dont have a luxary to miss the rotation or not know the fight mechanics beforehand. Always put a phasewalk according to boss movement ( like tfb first boss) or incase of pushback ( ev first boss ). You can compete deception with every other Class in Hm but for NiM i would recommend to learn hatred as well. There is 1-2k dps difference in the fights and hatred mobility is more advanced.
You can type assassin dps pve 4.0 parse on youtube.there is a great video about rotation.