i still dont see guren win against gaara. she could cristalize the first few attacks, but afterwards? she has by far not that much chakra, as gaara has.
the strategie deideira used would only work if
1. the bugs dont die in the sand, by pressure or by choking
2. shino can controll them so far that they dont eat the chakra before he tells them to, otherwise gaara would lose control about his sand and the bugs would never get close
3. gaara would use the sand of his shield, to first attack, and afterwards to defend. this would be only given in the situation that gaara is attacked by something his attacks cant reach and which is extremely fast (sand is faster than the bugs, i dont believe that shino could've traced deideiras bird) after attacking something which is extremely hard to hit and what his area-of-effect-attacks cant hit. since shino cant fly, gaara's attacks work against him, so using his ultimate-defence-sand isnt needed.
gaara can flood whole areas with his sand, how can shino escape this? how can his bugs escape an attack like the sand wave? strategie is important, but it wont let you win against an enemy who has all advantages at his side. a seal cant beat a white shark.
shino had fought in two matches against enemies who were rather bad. the sunagakure nin was wiped by sasuke within seconds, even chouji was a match for him, and kankuro never was a real enemy for anyone who wasnt foolish enough to be catched off guard by him.
guren, again is a filler char, and shino had weeks of preparation against her, knew her techniques and even adjusted his weapons against her with something we never saw in the manga. it wasnt really fair.