I think Gaara is a top 10 caliber fighter. Not saying he would definitely be put on an official top 10 list, just that he's top 10 caliber.
While it was a dual effort I see what you mean. Gaara can do the same sand coffin technique on his own. While it won't be as strong as Shukaku's, on the other hand how many fighters not named Madara could get out of it?
I'd put Gaara under Itachi, Madara, and Sasuke because their Susanoo would protect against the sand bullet trick.
But if he does that sand bullet thing and gets his sand in their system against anyone else, they are done for.
So yes he's top 10.
People need to realize that Naruto rankings don't always reflect that you're absolutely better than someone who's ranked under you. Hashirama is ranked above Itachi but if he gets hit with Totsuka it's game over. Some lower ranked ninja have moves that could potentially beat those who may be ranked higher than them and vise versa. So again, I'm simply saying Gaara is top 10 caliber, because that sand bullet barrage+sand coffin combo would be enough to beat some of the other top 10 ninja
