Of course, they don't cause damage but are very annoying. Look at the several times Itachi has used his crows against his opponents. They are annoying, distracting and obscures. It's not about he could kill them that easy because they're very nimble. This is the reason Itachis crows are always very useful.
And don't worry about Itachis Genjutsus, he was always able to catch his opponents in his illusion although they were aware that Itachi is a genjutsu specialist. He can cast Genjutsus any time and provoke it. Coming back to the crows, through them Itachi can also use Genjutsus.
Itachi doesn't have his Genjutsus and Mangekyou only. He is also very fast, can use elementary techniques and things like exploding Kage Bunshins, he makes very good use of weapons and is very smart.
I seriously can't believe that Deva is in your eyes superior to Itachi, but it's your opinion.