I didn't know you could poison the goblins

another thing I need to try. But what I can say is, almost all battles in the game are uphill battles and you will always be outnumbered, so better get used to it. The goblin camp is quite doable on tactician, just make sure you are at a decent level (4 works very well), use everything you have and make sure you are in a good position. Using the environment, elevation differences, surface effects and so on is an important part of the game. And remember you can take long rests after every fight. I did Minthara first, Gut second and Dror last.