Wierzyliśmy Ci do DZISIAJ sounds better
I agree with you BenYoung84, "had" is impossible. The best translation is "We have believed you", that is to say present perfect.
I removed the "had" variant.
Is "trusted" wrong?
That's "ufaliśmy" / "ufałyśmy".
we did believe you until today
The corrected translation sounds clunky in English. I think. We had believed you until today. We have believe you until today. ... crap, now not only can I not speak Polish, I am forgetting English, as well.
No that was a bad idea. You can't combine past perfect with "until today" - the present.
Ubtil today we believed you. Why is this wrong?
We could argue that that's "Do dzisiaj ci wierzyliśmy", but let's not split hairs. Added.