So I've been having some trouble in the Climax at Denerim, but luckily I had a seperate save at the camp site before shit went down so I've been able to go back and level up some more.
 
My question is though if donating to your army does any good. Do they just get new weapons, new armor, maybe more numbers? And while we're at it, is the difference even enough to actually bother with it?

I heard there's more of them, and a better selection of them.
 
Although that's only on the grapevine, I've not done it myself. I just keep giving them my deathroots and keeping things that can be turned into healing things.

I spent about two hours gathering money and stones and runes and the like but it doesn't seem to have had any effect.
 
I might go back and dump all of my funds into the Redcliffe troops, but I'm doubting if it will do any good.

What level are you?  Which part are you having trouble with?

GIving to your troops increases the numbers available at the final battle- I maxed out at 50 per army and 12 mages I think. Helped a little bit, but not a huge amount.

" GIving to your troops increases the numbers available at the final battle- I maxed out at 50 per army and 12 mages I think. Helped a little bit, but not a huge amount. "

I wouldn't worry about your armies too much, it will be a decent party setup that gets you through.  You do have a healer in your party?

Yes I do, and I just now got past the part and actually made it to the second floor so far.