My experience so far:

Wildhammer Clan (Twilight Highlands)

2.5/5 are collection quests. One kill X and one escort quest. The orc token quest drop for every character, you just have to IWT loot them with everyone.

Therazane (Deepholm)

3/6 are collection quests. Two kill X and one blow up Y mushrooms.

Tol'Barad

Different quests every day so it's hard to say exact numbers. Maybe a 70/30% split in collection/kill quests?