His information is fairly accurate.

This is not what you are doing though. You are grouped and killing the mobs yourself.
Umm he says 1 character is benifited by having 2-3 characters out of group (thus they get no exp) helping kill the mobs for the 1 character, as long as those helpers are not more then 10 levels above you.

I use 4 groups to "help" one group level. The 4 groups also get no exp like the single character helpers yet they help kill faster, of course you agrue its way overkill which is true, but the point is that I run though mobs like they are nothing and kill everything in the vicinity.

I am grouped becuase I level 5 at a time to take advantage of the group bonus. Its the same as what he is doing because I am able to kill mobs faster with 5 groups then with 1 group. Sure it dosnt scale as 5 guys helping a sinlge guy but its still the same.

I do better then what he says cause I do get the group bonus, AND I can aoe. If he has just one or two or three helpers he might not be aoeing, although with the right classes I am sure he would be.

If his math is sound then basically what I am doing is fine. Tag Boosting is at least as fast as Questing or Instance Boosting, if not faster.