I have definitely used Magit in situations where it was the only use of Emacs, working on the version-controlled content itself in content-specific tools such as Xcode or even MS Word.
Yeah, tig is awesome and I use it exactly for this use case.
For what I see, magit is way ahead when it comes to the feature set, but tig has the killer feature of having a completely flat learning curve (and I say this as an Emacs user): 1) type tig 2) use arrows to move between commits and page up/down to move within diffs. That's all!
I personally use magit, which solves this problem across all of git, but it's tied to Emacs.
tig is a git log browser I've heard good things about that seems to handle this use case very nicely.
You may also be able to pervert less into making this easier, e.g. by using lesskey(1) to add a keybinding that runs `git show $(xclip -o)`. I don't know how wise that would be.