Unfortunately for the Ninjask-->(Armaldo, Rhydon, Torterra) strategy, my own bulky Torterra walls all of them even with attack and roars them out and ALSO sets up Stealth Rock to limit Ninjask's effectiveness.
766 Atk vs 339 Def & 394 HP (80 Base Power): 390 - 458 (98.98% - 116.24%)
+2 Armaldo X-scissor vs Max/Max +Def Torterra. 100% OHKO with SR
788 Atk vs 339 Def & 394 HP (120 Base Power): 400 - 472 (101.52% - 119.80%)
+2 Rhydon Megahorn vs Max/Max +Def Torterra. 100% OHKO no matter what.
696 Atk vs 339 Def & 394 HP (120 Base Power): 264 - 312 (67.01% - 79.19%)
+2 Torterra Wood Hammer vs Max/Max +Def Torterra. 2HKO
So while, yes, ideally you would get Torterra in there at first sight of Ninjask, a smart player would wait and weaken it first, since you said you aren't running Max/Max+, you probably won't be taking these attacks very well regardless.