Correct. If your village is going to get nobled no matter what you do, you may as well put the troops to good use before they disappear.
If they are defensive troops (spears/swords), you can use them to help block the incoming army, so that the player attacking you takes troops losses. If there are too many incoming troops for you to block, maybe a friend who also has incoming *sooner* than you can use your help temporarily.
If they are offensve troops (axes/cavalry), you can use them to attack your agressor. That only works *IF* your troops reach his village before his noble captures your village. If your troops are defensive, they will do more damage to your enemy if they stay in your village to defend you rather than being sent as an attack.
If the world is young, you are alone, and you are surrounded by agressive, hot-blooded players, and if you have no hope no matter what you do...
You can always pick a new fight with someone who is powerful and who is not a friend of your enemy. Send your troops to attack this neighbor and mouth off to him. He will likely retaliate by attacking you back. Only.... by the time his troops arrive in your village, it will be your enemy's village now, and therefore you will have tricked someone into making your enemy miserable in exchange for the loss he caused you. You don't want to do this though if you still have other (safe) villages and don't want to be wiped out.
There's a lot you can still manage to do with those troops... but once you lose the village, they disappear.
Can you not use troops in another village to help stop the attacks?
