Remember only BMs cause adverse effects, not Hits (check out 1.3 on Blast Markers).
As Zombo says, Hits on shielded titans do not count where they do not cause damage and thus generate a BM, either in shooting or assault. From the rules:-
Quote:
SPECIAL RULE
5.4.1 Imperial Void Shields
Imperial Titans are protected by void shield generators. The number of void shields each Titan has is noted on the Titan’s datasheet. Each void shield will automatically stop one point of damage and then go down. Do not make armour saves for damage stopped by void shields, nor allocate Blast markers. Once all of the shields have been knocked down, the Titan may be damaged normally and you may make saving throws against any hits that are scored.
(my emphasis)