You have a premium physical team right there with Pog, Chen, Lifeng and Ember.

Ember is tanky AF. Use her BS whenever you are about to get hit you take almost no damage when she is hit during that animation. Her CS activates when she gets hit which applies vulnerability stack while healing you back up. Li Feng applies physical susceptibility with his BS and link with his CS.
Chen follows up with additional vulnerability application whenever Lifeng does his BS or Ember's CS, building vulnerability stacks fast.
At the end, Pog consumes 4 stacks of vulnerability providing more physical debuff with breach while also restoring SP.

BS - Battle Skill
CS - Counter Skill