A decent build, and a pretty good guide.
Assuming he spent all his 20 points to get that build.. IMO it seems abit underpowered.
I have been trying to create a good build with Regulus myself. I play with a mate who uses Torch Bearer and without fail, every match he will out level me, but atleast 2-3 levels and have a much higher damage amount.. often 1.5 -2.0x
I found going Angelic Fury from the start, followed by health/stat (the bottom one), then basically bounce between the 2 favouring health/stat 1 level above angelic fury, and adding in atleast 2-3 levels of Sniper Scope well before maxing out the other 2. Then if anything else adding abit of Mark of the Betrayer to a little extra damage up close, or sniper for some long range plinking.
Then save like a mofo and go for either Mageslayer or Ashkandor, I generally go straight for Ashkandor and thats without buying any other high level items like godplate for example. Just a couple basic to mid health/armour/mana items to get me buy.
The only real issue is mana, and even that only requires a RTB (return to base) once every few DG kills at the very least as you can often pick up their mana scrolls.
Once you have Ashkandor, then focus on getting Mageslayer or Godplate (if your getting whomped a bit), then ideally fathers ring.
This can generally be accomplished all by around level 13 or so.. sometimes with the except of fathers ring, depending on how well your going.
But you will have over 6k health around 5k mana (might need one of the higher level helms as well) just shy of 3k armour, attack time reduction of I think around 68%, and damage of 550-620.. or was it 620-700.. not sure exactly but its alot.
On top of that you will crit fairly often for anywhere from 1500-2500dmg, and you can safely take down a high level Rook in less time than it takes to read this last sentence.
Now im out kill/level/damaging him. A nice outcome 
But I guess there are advantages and disadvantages to every build (to an extent) all depends on who your playing against and map..etc..
(woah big post... /ramble)