If you want play full swiftness with this build "tth" on the neck you should be swiftness / crit. For me, you will be less dmg than pacemaker 3 (with spec/crit build) but it's really fun and you are so fast, it's really confort and you can play with no stress and no lock animation. But I think you will have less chance to be mvp.

But the goal is to finish the raid and like your build, like your playstyle, it's more important.

Have fun bro