In my current game, I have been in a position to win but the other close player has basically pulled a rabbit out of the hat by lucking into a Navigator and Martyr with his last few specialists. He has it aimed at my mine and without a Pirate in range, there is absolutely nothing I can do about it.
I saw this being used multiple times in my previous game (not against me, thankfully, since I was out of range of the player using the strategy) and it seemed to be a real feel-bad strategy.
The effect of losing an entire node (especially a mine) is far too great to not have any viable counters outside of randomly lucking into a Pirate. At the very least, I feel like Sentries should be able to destroy 0-driller subs with specialists onboard.
I also feel like you should be able to initiate combat with subs that cross paths if you get the timing right, which does not seem to be the case for any sub with an altered Navigator path.