It doesn't need to say "armies", because C'Thun's armies are mentioned right after that. And guess what? The armies were the first concern for Alliance and Horde, not whatever power the Old God had. Through its armies C'Thun was going to storm Kalimdor. I mean, that sucker can't even move.
C'Thun needed to build up massive forces if the Old God desired more than just wait for 40 people to beat its ass. Building up its own power/stamina/strength/whatever? You weren't even able to give a proper justification for that besides a baseless assumption that breaking its restraints took something away from him, something that even Chronicle doesn't support, all the book says is that a lot of time, thousands of years would have required for the Old Gods to achieve their freedom.
I mean, you have to justify your argument with headcanon and still have the audacity to claim that the description is not up to interpretation? Give me a break.
Lol. Strength =\= Power but Strength = Armies........
You have got to be kidding me. Krusty Troll.