Yes I understand that. Blizzard has also said that the Mastery system will be put in place to give them another easy knob to use for tuning trees better. So I can understand the first two Mastery bonuses of a tree to be things like increased Melee Damage and increased Melee Attack speed, because those are both stats which are easily used to change a tree's performance.
I was pointing out the discrepancy between our third tier Mastery bonuses and others. Because at this point in time, it looks like we are going to have two different types of talent trees. One type that has boring Mastery bonuses but interesting talents and another that has interesting Mastery bonuses but boring talents. This may not be (and probably isn't) what Blizzard is going for but that's what it looks like at the moment.
Of the ones you listed, at least 2 of them aren't really a good comparison. Blood DKs is their new prot tree, so that's their tanking bonus. It's taking what already exists (they can heal themselves with certain attacks), and applying a "shield" like effect. So it's trying to copy the current druid bubble giving all tanks a (psuedo) shield.
The shadow priest one, is maybe only interesting as a graphic. It boils down to "increased shadow damage", which is just as uninteresting. Likely able to keep it up to practically make it passive, just need a ramp up time.
As for bonus swings... Since they want to take out all the uninteresting weapon specs of passive damage with maces/fists/daggers, and want to make sword/axe specs extra swings a talent that applies to any weapon... That would be the means of the more "interesting" talents. Only thing could be Arms able to double dip the mastery and the talent, it'll likely be tuned around for that.