Tablet is always good on bomb since you have no escape mechanism and EVERYONE WANTS TO KILL YOU. SOTM is also not bad because it will generally cause chaos in teamfights- just about no one is tanky enough to stand around in the napalm so they pretty have to scatter if you ult down the middle of a teamfight. It also has a pretty easy build up that gives much needed hp.
Sotm and spellshards are excellent pickups on bombardier, but it is worth noting that they are also TIME SENSITIVE PICKUPS. Sotm at 25 mins or earlier is a real kick in the cojones, but after a while the devastating effect will taper off (not exactly a surprise). If you find yourself playing a supporting role (roaming around, placing wards, stacking) then going for these dps increasing items may not be the best choice since you may not get them early enough to get the most concede for your buck.
PS: Bombardier can rip through triple stacked jungles as if they were paper. Just sayin.