If you do a lot of engagement shoots then yes - if not, I think it would be too difficult to work it into a wedding day unless you always work with an assistant and 2nd shooter - the other issue is carrying around another piece of expensive kit that is going to be off the camera most of the time.
It is a highly specialized lens - so I would recommend purchasing a used copy as they are often very lightly used.
I can also personally report that the lens works on a Sony A7Rii and no doubt the upcoming A9 - so from a silent shooting wedding perspective that is a nice feature.
In my opinion, this isn't a wedding day lens as it is too restrictive - but the images it can produce, as everyone knows, are simply incredible.
I don't want to sound like a Sony Fanboy, I own a Canon 1Dxii and a few other Canon cameras, and also shoot weddings, but from a wedding perspective, I think the Sony A9 is potentially a real game changer (silent shooting, good battery life, etc) that I think you might just see, over the next 2 years, a lot of Canon gear go for sale.
Hockey and wedding photographer. Favourite camera / lens combos: a 1DX II with a Tamron 45 1.8 VC, an A7Rii with a Canon 24-70F2.8L II, and a 5DSR with a Tamron 85 1.8 VC. Every lens I own I strongly recommend [Canon (35Lii, 100L Macro, 24-70F2.8ii, 70-200F2.8ii, 100-400Lii), Tamron (45 1.8, 85 1.8), Sigma 24-105]. If there are better lenses out there let me know because I haven't found them.