Do Titan Killer weapons bypass Void shields/Powerfields/Holofields?

It depends on what is being shot at. If a titan Killer weapon hits a target protected by Imperial Void shields or Ork Power-fields these are stripped first, any remaining hits going straight through the Titans armour.

Eldar holofields are slightly different, as they may deflect the titan shot on a 3+. If the shot strikes home, it still causes the relevant number of hits on the titan (which it's normal armour cannot save).

In both cases, BMs for hits are only placed if damage is caused to the titan. (Corrected)

So, if a pair of DeathStrike missiles are shot at a fully shielded Reaver causing 5x and 4x hits, the first missile would strip the shields with one hit striking home, while the second missile would then reduce the Reaver to a single DC. (And the titan would break having received 6x BMs)

If the same happened against an Eldar Phantom and the holofields saved against the first but failed to stop the second missile, that would reduce the Phantom to 2x DC (leaving the titan with 5x BMs so not broken).

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Sir Hemry Newbolt

This part is incorrect.  

A target unit always gets 1BM for coming under fire, even if it has shield/fields.

Hits absorbed/deflected by shields/fields don't cause any extra/bonus Blast markers, such as via disrupt.

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Ah.

Somewhere along the line, I had thought I had read that Titan Killer weapons bypassed fields. My bad.  

Thanks for setting me straight.  

My bad - another case of 'digitus interuptus' between what I wrote and what I meant. I have corrected the offending line

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Sir Hemry Newbolt