I've given up dry hopping with leaf, though if I did I would either (1) use a bag and weigh it down with a spoon (some people squeeze the bag too), this works whether you are siphoning off or using a tap, or (2) have some sort of hop strainer/filter attached to the tap (this won't work with pellets).
What I do now though, and it hasn't given me problems, is chucking the pellets in and they fall to the bottom during the cold crash. I just siphon off carefully into a bottling bucket, so what little does pass through the siphon ends up settling the bottling bucket. I'll pulled off some pretty big dry hopping like this, and I'll do the same with my current brew: 100g Amarillo, 100g Galaxy and 30g Simcoe.