"Find me ... cattle" quests.

I just wanted to suggest that the Village Elder either accepts the required amount in smaller doses, like one or two at the time. (If they don't already) and that one can fuse multiple herds together, else these quests simply are a pain in the arse.

Agreed, it's not fun to drive them, they should just follow you in my opinion at the very least though they could slow you down.
What would also be nice if the lord didn't **** off elsewhere until you did it.

Be ware, you are talking about different quests.

However, the "bring me cattle" quests of marechals of the army are very hard to me. The amount of cattle (20-30) is very hard to get (often 0-5 cattle in a village), very expensive (500+ per head), or very honour/friend costy. And the time given is ridiculous (a couple of days), considering how much villages you have to visit and the difficulty to drive the herd and find the lord again.
Result for me: Quest failed, 21 cattle i cannot do anything from but slaughter them and cry for the 10000+ denars lost.

Yes, when I am told I can steal up to 10 cattle from a village, Im lucky to get more than 1 and I had 4 in looting.  And you have to wait a long long time before trying the same village again.  Its just too difficult.

Grimage, what I said in the OP works for both quests, even though I only had the village one in mind. 
Also, why PAY for them?