A thought crossed my mind (doesn't happen often), so I decided to try out some numbers.
Currently, using all imbued armor, my sampire is at 186 stamina, all 70s, etc. Thought about doing assassin armor per this thread. I figure if I supplement assassin armor with all imbued armor, I can get to 177 stamina (125 + 20 from set + 32 from 2 jewels and 2 other armor pieces).
The imbued ornate I'm using now has 25% SSI. Before long I'll probably step up to a 30% SSI ornate, but I've been too lazy to farm the essences so far. Assuming the stratics calculator is correct, at 25% SSI, I can go all the way down to 160 stamina from hits before my swing speed drops from maximum. That's a net loss of 26 stamina. By comparison, with my hypothetical assassin-based suit at 45% SSI and 177 stam, I can drop to 120 stam before swing speed falloff, a net loss of 57 stamina. That's not using jackal's collar (I like being medable in case I get in a tight corner).
My thought (wrong apparently) was that the amount of stamina which would have to be sacrificed for assassin's armor versus an imbued suit would counteract to a degree the swing speed bonus of the set. Seems that's not the case. Just thought I'd share in case anyone else wanted to see the numbers.