Stacking Runes of Warding

I was reading ELDAR ONLINE the other day looking for some insights into other peoples experience running corsairs when I came across a rules interpretation that left me scratching my head.  It has to do with the relatively recent FAQ update for the Eldar.  In particular it involves an Errata for Runes of Warding which reads as follows:


ERRATA
Page 26 – Runes of Warding
Change the last sentence to “All enemy Psykers must
roll an extra dice when taking Psychic tests, suffering
Perils of the Warp on any roll of 12 or above.”

It was the general consensus that with this new errata that Runes of Warding would stack.  In other words, taking two Farseers with runes of warding would force the opponent to roll 4 dice and anything over 12 would count as a peril of the warp.  If this is the case does it change the face of how Eldar are to build lists, or at the minimum give their 4th edition codex a well needed boost?

If an accurate interpretation of the rules then I would suggest that the Eldar have received a boost against Grey Knights for one.  With Grey Knights accounting for a large segment of armies played over all it would appear that the boost to the codex is more than just trivial.

As it stands, if this were the case, I would be looking to tailor an Eldar list then to include Eldrad and a Farseer with RoW, Stones, Guide and Fortune.  Three DAVU Falcons then with holo-fields, stones and EML's to form the core of my army.  A possible 4th troop choice of storm guardians with warlock, embolden, fusion guns and spear to boost Eldrads powers.  Fill the list out then with Fire Dragons in wave serpents and perhaps a seer council.

Then again, perhaps this is an erroneous interpretation of the RoW rule and that only 3d6 dice are to be rolled when taking the test.