That's how they perform. Personally I'd prefer it to having large leaves around for months as with tulips and daffodils. I usually plant my Allium bulbs among perennials so the foliage dying back isn't as obvious.

Thanks Carol,
That is what I did: planted them on the background. The leaves turned brown before foreground perennials were high enogh to hide them. I also do not cut leaves until they are completely dead. So I guess I have to either move them back even more or to get rid of them...

I plant mine along the back of my perennial beds and I really never see the dying leaves. By the time they bloom the asters, salvia and every thing else are up and taller than the leaves. I think if I didn't hack my asters back in half in mid-late May I may not even see the blooms.

So I guess I have to either move them back even more or to get rid of them...

Or perhaps go ahead and cut the leaves back as they die off. I'm surprised that your other perenials don't get high enough to hide the foliage -- the foliage seems to wilt down to the ground quite quickly once they begin to die off.