Great spec for starting out, the one Squirrelnut advertises. Your survivability should be good and your threat from dps nice and high. I have tanked with a warrior since the vanilla game, but found that the tweaks to the classes and encounters as the game has evolved has turned tanking into a new and different beast indeed. The 15/5/51 spec is great all around, even if it felt a little off to me and I ended up tweaking it slightly.
When you get experience tanking under different circumstances, you may end up tweaking it towards your own preferences. Could be that you prefer a block-heavy spec and gear set for tanking a lot of trash in heroic instances. Could be that you like high avoidance against those heavy-hitting bosses. Could be that all your dps in your groups are cloth casters or melee plate - it all ends up influening how the cookie-cutter 15/5/51 spec feels to you.