I agree with you: your lineup is top-notch, but your pitchers look like they'll be in the middle of the pack. Nothing wrong with that, of course - you can win your league that way, but a bit of help on the mound wouldn't hurt.
The problem is that pitching help might be hard to come by, since your bench doesn't give you too much leverage in terms of trading bats.
Let's see... Morris and Mulder are studs, I don't like Dempster as much as most forecasters do, Lidle and Halladay could be very nice but are no guarantee, and I wouldn't touch Hampton, even if you're just planning on using him on the road.
Leskanic's situation is extremely hard to predict - he may well be the Brewers' primary closer later on this year, but a solid performance by DeJean or one of several other options could change that. Hernandez will get you decent saves, even if his other numbers won't look good.
If I were in your shoes, I'd drop Hampton and scour the free agent list for either a reliever who might fall into some saves, such as:
Looper, Gagne, Herges, Nunez. If no saves candidate is available, pick up a starter who can put up respectanle whip and era numbers.
This may seem like sacrilege, but I'd also ask around to see what you could get for Giambi. In all probablity, no offer will be high enough for you to accept, but asking around never hurts, and I like Johnson's chances this year. You could, of course, go the other way around and shop Johnson. If you could get a mid-tier pitcher (starter or reliever) for him, you'd be ahead of the game. Shopping Edgar Martinez is also an option.
Of course, you can always wait for the closer carousel to turn again and try to pick up saves that way, but putting your ear to the ground and seeing if any decent trade possibilities are out there can't hurt...