Do you want your champions to live? If the answer is yes then Monument will help them do exactly that. One thing to keep in mind is that he will not stop 1 shot mechanics. So if a champion goes from 0 to dead there is not much Monument can do other than mourn the loss of his teammate.
His damage is decent. Skill 1 receives bonus damage from Defense while skill 2/3 directly scale from it. So it is a good idea to stack defense. While attack will help with Skill 1 it will have no effect on skill 2/3. It is for this reason I recommend a heavy defense build with a dash of resistance and accuracy.
All-in-all Monument is an excellent addition to PVP and PVE teams looking to well live.