Slicing vs. blending
Usually, slicing things up is better than using a blender.
Blending fresh herbs might save you time, but it's generally not a good idea.
Processing herbs: slice or blend?
A thread on the medicinal herblist a few days ago:
Yael: Aren't you using a coffee grinder to chop your roots or to reduce the volume of a herb before maceration?
Jim McDonald: It's real tedious work, and maybe a bit fanatical, but I figure I'm not completely off the wall, both because I know Henriette individually chops her hawthorne berries (well, I suppose we both could be fanatical) and because I'm not so rigid about it that I won't use a coffee grinder if it makes more sense.
Do you know, I didn't even consider using anything but a hopefully very sharp knife on my hawthorn berries. Those seeds are big, and hard, and are quite likely to break any blender you'd try them on.
Sure, I could've dried my berries whole, unhalved, but that would give me low quality herb.
As to fanatical, I don't blend any fresh herbs at all. Not for tincturemaking, not for drying. There's reasons for that:
Tincture: blended will give you much more inert material, and therefore much more "sludge", much more bottom muck in the tinctures.
Drying herb: well, I suppose you could layer the mess that comes out of a blender and try to dry it, but cutting things up is ever so much neater.
Dried herb: I powder dried rosebuds (certified organic, bought) in a blender before I make my rose salve. That way I get more surface area, and can capture more of the fragile scent in the oil.
And I use a blender to powder dried herb before I percolate - you need powder for percolation, and for maximum quality it's best to powder things yourself.
But for macerating tea, tincture or vinegar? There's no need to powder things up. Nor is there a need to powder things for your usual infused oils (rose excepted), be they macerated (I don't recommend macerating oils) or on a waterbath.