To be fair, UBW does have the virtue of requiring a Ten Count chant to activate, which gives a big opening to counter it before it begins. As far as tracing goes, this thread should give a better idea on how limited its capabilities are: https://www.reddit.com/r/fatestaynight/comments/4bui08/comment/d1cj0v8

That being said, I don’t plan on pulling an Excalibur Image or anything of that sort, and EMIYA is already at a bit of a disadvantage given that it’s a Great HGW since he can’t make a copy of Arondight. Really, alot of EMIYA’s strengths comes in his versatility from tracing, and even then, he’s still held back a few paces due to his stats and lack of mastery. If he and Cu continued to fight in the VN up to the last person standing, EMIYA is bound to lose, even with Cu holding back. With his kit as it is, without nerfs, he’d be a good C-tier Servant, and it’s made apparent in all three routes of the VN.

That being said, I don’t plan to make an argument out of this, I’d just like to point out how actually balanced EMIYA’s kit is compared to the rest of the F/SN cast. If he does get nerfed after my explanations have been given into consideration, I might go with Arash after all depending on how severe the nerfs are.