[jivemi]

Well I dunno Andrew, the same stuff happens to me a fair amount of the time. Not much you can do against arty and air bombardment except disperse your forces (although not so much as to lose unit cohesion) and keep them moving to fake out AI plotting. Sometimes flak units help against airstrikes but just as in RL they're usually "ineffectual" or unreliable.
So spread your guys out a bit and keep 'em moving--within bounds of caution to be sure.

Using bombardment against the AI it's considered best to focus on one or a few targets at a time. Concentration is the key; better to plaster one unit or position than to simply harass a bunch of them with little more than suppression. Also go for stationary or slow-moving targets like pinned infantry or AT guns, especially if they're in the open. (OTOH sometimes you can make an informed guess when spotted enemy tanks will arrive at, say, a crossroads; that's the time to plot multiple airstrikes on juicy armored targets.)