I'll say yes, Crobat damage output only matters if it's running Life Orb and 252 atk (where it can OHKO Latios and offensive Gyarados/Nite after SR), so you don't really lose anything by lowering its speed without much atk investment, and the extra bulk makes it easier for you to taunt and roost stall things like Ferro's Gyro ball, or just not let Gyarados set up at all (or even take a +1 waterfall from the sub bounce gyara set after SR, asumming 232 hp /0 def = 68.3% - 80.5%). Like you said, Scarf Toed is really rare, and besides I don't really think it can do much against the rest of your team since it's stall, and even then, 232 hp/ 0 spD Crobat can also take an Ice Beam/Hydro Pump under rain after SR.
So to summarize, Crobat doesn't need full speed unless you're running also full atk.
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