OK, I'll confess; I have a 45-70 barrel for my Encore. In addition I carry a 9mm Parabellum and a 380 Auto. I consider the 380 Auto pretty underpowered but it best for concealment with certain types of clothing and is better than nothing. I consider the 9mm Parabellum more adequate but once again, it's not my first choice; if clothing permits, I'll be carrying something like a 40 S&W, a 357 Magnum, a 44 Magnum or maybe even a 460 S&W Magnum.
I believe the 45-70 if perfectly adequate for deer, groundhogs, bear, etc. The ridiculous thing is the same question as to whether it's a "dangerous game" cartridge comes up over and over with pretty much the same responses. The fact is are that in the current crowd of big bore cartridges (I'll include the 375 H&H Magnum here though I know in Africa it's considered a medium bore), the 45-70 is not going to be taken seriously as a dangerous game cartridge now or ever. Keep asking the same question and you'll get the same answer. It's also a fact that professional hunters in Africa have let clients shoot dangerous game with much less potent cartridges (even down to 6mm bore size that I've heard of) but that doesn't mean things like a 338 Winchester Magnum will ever be seriously taken for a dangerous game cartridge.
So, give the 45-70 the rest it deserves after all these years.
As far as black powder and sticks and string; they still use those on dangerous game but it's a stunt. I will start to be impressed when some intrepid bow hunter AND his PH go after an elephant both armed with bows.
There was a show on several years ago in which a bow hunter shot a grizzley. The grizzley got away so of course the next day they went to follow it up. Guess how many bows were in the follow up entourage? That would be zero.