There are times when you'll be a dog with top or middle set against an excellent draw. Here's a hand I had last night (I had the draw).
http://twodimes.net/h/?z=1214465
pokenum -o ad tc td 7h - kd 8s 9s js -- 7s ts qc
Omaha Hi: 820 enumerated boards containing Ts 7s Qc
cards win %win lose %lose tie %tie EV
Tc Ad Td 7h 320 39.02 500 60.98 0 0.00 0.390
Js 9s 8s Kd 500 60.98 320 39.02 0 0.00 0.610
This is the only time in memory that I've seen a draw be such a huge favorite over a top or middle set. Generally, a really big draw (multi-card straight draw + flush draw) will have at most a 5% edge. Even these draws are somewhat rare. Top set is a push push push hand barring really exceptional circumstances.
With two callers, most likely some sharing outs, you're probably about a 40-50% favorite on the flop and 50-60% on the turn. Get as much money in when you're ahead.
Here's the set up (picked your sidecards are random) in which you are in the most trouble:
http://twodimes.net/h/?z=1214477
pokenum -o qc qd 6d 8s - ah 8h jc 5c - ac kc ts qs -- qh js 5h
Omaha Hi: 666 enumerated boards containing Js Qh 5h
cards win %win lose %lose tie %tie EV
8s Qc Qd 6d 269 40.39 397 59.61 0 0.00 0.404
Jc 5c Ah 8h 209 31.38 453 68.02 4 0.60 0.317
Qs Ts Ac Kc 184 27.63 478 71.77 4 0.60 0.279
You're getting a nice chunk of equity in the pot. Blast away and be wary of the river.