Well, I just checked, the official listing for the ultramarine chapter, if it's any indication, gives 25 predators, 9 Whirlwind and 8 Vindicators for the whole damn chapter. So if you have a force based around a battle company (2 Tactical detachments, 1 Assault detachment, one Devastator detachment), you should be able to get, on average and rounding up, 3 predators and a single whirlwind.
I certainly wouldn't call a single whirlwind "Artillery formations". Even if you were to field 2 Battle companies (that's about 4*300 + 2*175 + 2*250 = 2050 Pts, 2150Pts with the captains), on average you would only get 1.5 tank formation and 0.5 artillery formation. Saying they get skimmers is a bit misleading as well; Land speeder formations are not exactly a fair analogue to what is usually called skimmer in, say, an eldar or a tau army.
Get on with it, if you want your marines to be in line with GW background, you'll have to accept a lot of contortion. They are indeed like special forces or shock troops. A chapter actually has more thundehawks than predators (the ultras get 31 of those !)...
The background of marines stress their autonomy, true, but it also stresses that the main factor of their efficiency is actually fear and their ability to decapitate the enemy with a surgical strike before they have to face them as an army.
And examples about the Armageddon War are hardly going to prove that marines can do it by themselves when there are hundreds of IG regiments, a sizeable fleet and several Titan legions (around 6 legions actually!) engaged in the same conflict. The fact that they actually go in strength to take out specific strategical targets is actually getting some length to support what I am saying.
Don't get me wrong : I love to be able to field terminator formations, artillery, tanks and titans, air support and all that stuff, but when it come to marine armies, reference to the background are only going to get you so far.
The most important thing is that the list is about balanced, that it is fun to play and has a few options. I'm not sure removing options is the best way to balance the list if isn't viable to play without warhound or termies, or if punishing a player that want to take titans in an epic game is actually something that make sense at all. Reaver and Warlord are already too much of a gambit to be played in a usual list, lets not take away the only option to field WE from the marine for the sake of a background that is IMHO unsatisfactory anyway.
The background makes the Titan Legions, the Adeptus Astartes, the Guard, the PDFs and the Navy different entities, but if that should make us feel that taking aircraft or titans in an imperial list is in contradiction with the background, I say screw* the background.
*Actually, it makes me say something else, but I'm not quite sure about the language policy around here
