Right, you don't need to tip the doorman per bag. Tip the shuttle driver $2 per bag, tip the doorman maybe $2-$3 total, then tip the bellman who brings the bags to your room $1 to $2 per bag.
I travel with a total of 5. On vacation, we can make the first contact work for the $5.
To me, it's also about the class of hotels and the convenience. When you stay at the Grand (or even DLH), you are staying at a luxury hotel and should realize that the bellmen (wish there was a gender neutral term other than the antiquated bellhop) are part of the experience. You should also realize that unless you have a later check in, the bellman can help smooth things over and that they are generally giving a great service.
Paradoxically (and probably due to pay scales at different resort classes), I find the bellmen at the mid-class hotels more aggressive when I choose to carry my one roller bag that fits under my airline seat rather than have them bring it up to my room.