One option would be to change the martyr to only work on a "penetrating" blow. I have been wanting to use the martyr/nav in my current game (yes guys, I got it, so be nice) and it just seems OP.

I think requiring the lucky guys who happen to get the combo (which seems pretty likely over the course of the whole game) to plan ahead and send a large enough force makes for good strategy. Its a big ole nuke, it shouldn't just be a random free-bee IMO

Then at least there is a counter that isn't also solely based on specialist luck, if you prepare for it. If not, then you have no reason to complain.

I don't know if that changes the whole dynamic of the martyr too much though.

Still lovin the game!

Edit: i just realized what i describe is simply capturing the outpost. it sounded good though. only difference would be the destruction aspect, which might be usefull, but changes the martyr from "OMG WTF" status to"meh". It would be useful if say there is a key mine people are fighting over and you just want to get rid of it, for instance.