That's the amount of talents in the new Discipline tree that literally affect nothing but Power Word: Shield. Tier 4 of the tree is all talents that affect Power Word: Shield. Eight points on one tier dedicated to one spell. Because of this layout, the minimum number of points you can devote to improving Power Word: Shield while going up the discipline tree is 4, and that's only if you spend 2 points in a dedicated PvP talent.
As a discipline priest, having to take talents that support Power Word: Shield doesn't seem like a harsh penalty. It's sort of like having to take talents that support fireball as a fire mage. Of course fire mages don't have talents that specifically support fireball in the new talent trees. Frost mages have 4 talent points devoted to propping up frostbolt, and 2 of those are extremely optional and only borderline useful. Prot warriors have 3 talent points exclusively dedicated to Devastate, one of those being Devastate itself. Retribution paladins have 2 talent points that only prop up Crusader Strike (though there are three more that do nearly nothing else. Holy Paladins have 6 points to prop up Holy Shock. There are 7 talents to prop up Rejuvenation.
So why don't these classes spend a third of their talent points propping up the spell or ability they cast more than any other. It's because those spells and abilities are actually good in the first place. You don't need to spend 13 talent points to make it worth casting the spell that defines your role. For a discipline priest, the spell that the developers are claiming will account for 50% of our healing requires 3 talent points just to get rid of a 4 second pointless cooldown. Flash Heal costs about 50% more mana and looks like it heals for about 50% than the shield absorbs. Plus I can cast it twice consecutively on the same target. Instants are good and shields are good, but having 2/3 the throughput seems like a sufficient penalty. Similarly, I'm going to spend 2 points on a very conditional talent to let me cast it more often on the same target. Again, if I just need the throughput then Flash Heal is better at that anyway. Flash Heal can also critical, by the way, and effectively does so for times two because of Divine Aegis. Shield, on the other hand, even if it lacks the cooldown and the weakened soul, would still not be spammable because it overwrites itself if cast twice on the same target.
Take a spell that you would very rarely want to use and devote 10-13 talent points to it (since the last 2 are actually very bad) and you get a spell you'll want to use a lot. But similarly, force a spec to devote 10 talent points to a spell when they are picking their talents and you have to make that spell bad to begin with.
When I look at the discipline tree now I feel like it still suffers from the same problem it had in Wrath. A great deal of the three is there just to play catch up leaving discipline priests as relatively weak healers any time they are not throwing out shields. In the end the tree worked (mostly because some of the talents were drastically overpowered), but half the time it just hurt that you actually had to spend your points on what you were spending them on. I'm not ready to pass judgement over whether the current tree works since that would be silly (and one of the drastically overpowered talents is still there) but it still has far too many points that are there to turn one spell that is probably the weakest in the priest healing repertoire into the strongest.