Before templates, I could place 2-3 shift-ctrl clicks of my 4 main turret types (basic, mlrs, missile, laser) worth of turrets in a roughly triangular fashion around any hostile wormhole. More for home systems.. But that was my basic defense: 10 or 15 of each of those turrets. Now, I can simply and easily place that combination (in a more beautiful circle pattern, mind you) around a wormhole. One click per wormhole, plus a few to open the template. this, for me, is a time saving thing. (and I recently 'walled up' a 8-wh planet, mind you.. its a LOT of saved clicks)
yes, it is not as advantageous as planning out the defense with the expected direction of hostile movement, but its a hell of a lot quicker. Thus, its worth it for me.
Also could be used to build a selection of 'per planet units', like a rebuilder, mk1+2 power gen, research lab, and a forcefield depending on how you use it (in conjunction with a command center turretball, mind you)
Oh, and yeah - Wormhole defenses will often need to be suited per-planet basis. Theres no such 'one size fits all win-machine' in AI war - there are some good tactics, but often because they are flexible enough to work in most situations.
Sure, if you place 30 of each turret around a wormhole, theres a good chance nothing will get through, but at a good deal of material and energy costs, not to mention ship cap costs.