I'm not sure if this helps but...

Shock Squall is Stun and marches in step with most Stun spells rather than enfeebling effects in general. As of such, Shock Squall has higher magic accuracy than most effects and very few monsters have a native resistance to it.

Abilities like Diamond Storm and Tidal Roar are more comparable to Enfeebling Magic in terms of their mechanics. So, yes, anything that makes them more accurate will make them more accurate because it makes them more accurate. Except when it doesn't make them more accurate because you're at some kind of cap already, I guess. Magic accuracy is one of the hardest things to test due to multiple resist states.

All the same, it's not like there's anything other than Summoning Magic Skill and/or "Avatar: Magic Accuracy" to macro in for those abilities at time of activation, so why not?