Rubbish, it is a DPS loss. You're saving 3k MP for a reduce tank buster when the DPS windows are up, that is a loss. Unless you work with your team knowing when and not when to. Edge values way more over TBN when your DPS are using utility cool downs.
All TBN is good for is blocking Busters, auto attacks take too long or don't break in time the further we go with our Ilvls. HOS can fuel out consistently for a short CD, reduce a buster and reduce an auto attacks, plus AOEs. Or other words rotate around with no drawbacks, it isn't maths, it's common sense.
Always max DPS over the "reduce buster damage", not talking about casual easy content. Rampart/Sentinel are always back for the next busters, with the Invulnerable included. Only E4S really puts the threat at the moment to use TBN, other than that with 470 there's no need for it.
In the end Pld/Gnb will be top notch combo for doing larger DPS pools.