Well, yes and no. It depends on if the combat cards are shuffled back into the deck or if they are discarded. If they are immediately shuffled back into the deck, then they are functionally identical to a dice with an equal number of sides as there are cards in the deck. However, if you discard the card then this all changes because whatever result was on the card is taken out of play. It's the equivalent of rolling a six on a chart, and then saying that you can no longer roll sixes on the chart. It has a memory, which isn't something that dice support.
And that's where the line between Euro-style and Ameri-style tends to be drawn, as far as randomness goes. Best illustrated in the classic "Settlers of Catan", which eventually included a dice deck to replace the actual dice, because some people thought they were getting screwed picking the 2 and 12 spots, which never came in many a dice-rolling game, but were sure to appear once every 36 turns if each combination of dice was eventually "flipped over". This gets slightly altered by burning the bottom few cards and reshuffling (to avoid predictability once the deck runs low), which is what I'd expect Runewars to do as well. Cosmic Encounter does this with its Destiny Deck too.
Since each Fate card contains outcomes for each class of unit (infantry, elite infantry, mounted, heavy), plus some unknown-use number at the bottom, it'll be much harder to predict that any given unit will get good or bad results, even with the deck running low - because you're not sure how many cards will be flipped before your chosen units' initiative will come round.
I guess cards make it easier to prove the reliability/unreliability of outcomes whereas dice would take more trials than a typical game might have to come to the same conclusion, empirically.