I actually think that the two easiest holes on WGT, assuming low or moderate winds are probably the first hole at Kiawah, I almost always birdie it or the 1st hole at St Andrews. The first at Kiawah is wide open and all the putts from 10 feet are pretty simple. The 1st at St Andrews is wide open and usually only a half wedge and a fairly flat putt.
All the par 5's are pretty much birdie holes on every course so I ignored them. My point of view is the Legend tees so you might have holes that are easy from other tees, like the 13th I think at Kiawah, easy birdie until you get moved back 100 yards to the Legend tees.
Tier has a lot to do with it, some easy holes for masters are tough for legends.