Bombs as UnitAura triggers work fine, it's just the UI kind of sucks in explaining how the matches work.
In short, you'll need two matches. Matches are basically combined as Or (|) checks, so we're looking for Frost Bomb or Living Bomb or Nether Tempest.
I've rolled up the two bombs into a single match,
and the second one covers Nether Tempest.
In 4.x the way you'd do this is by using / delimiters between the effect names, which don't work now (for various reasons). The advantage to using this is you can configure each match independently, so you could set it up so that it matches YOUR Living Bomb or ANYONE'S Nether Tempest - if you're weird like that
I'll add tooltips and help text to that part of the UI soon.