Multiplayer or singleplayer?
SP:
heavy depends on your difficulty. Tanking is easy in low difficulty (i played on 2nd diff). at Post Human (4th), Tanking can't be done because the enemies shoot accurately.
what tactics to use depends on how you use weapons and powers.
but in Cryis 2, there is only one correct tactic: modify everything, and then i mean EVERYTHING, to how you feel at that particular moment. adapt.
choose the suit modules that fit your style of play. choose your attachement according to how you play. use your suit powers according to how your play. that is the beauty and power of Crysis 2.
for the Single Player, the easiest way to semi-tank, is the HMG. powerful against all foes. you do need a proper armor module like deflection or armor enhance.
sneaking works, but only in some cases. Cloaking is mandatory in Post Human since you WILL be shot at and regaining health and energy all the time doesn't work nicely. use Cloak to relocate. pick a good spot. fire from there.
i use a DSG/Marshall (silenced) combo. i can cloak, pick out the enemies. i can armor up and get up close and personal, or i can stealth toward an enemy and blow his head off from 1 meter away.
it all depends on how you want to play. if it gets boring, think of a new approach, adjust your modules and attachements and go play, and change modules if they don't work the way you need them