Tips for successly outpost attacks:
1) DO NOT solo attack an occupied outpost. You will probably have many troops die.
2) Garrison or Rally leader will be the player with the largest rally size to allow the most troops in the garrison. The Garrison/Rally leader will use strongest gold tier troops like Jabel, Saul, Helga.
3) When dispatching to a garrison, your first hero should be a hero like Gordon, Howard because they providea health or defense bonus. Heroes used for attack and lethality like Chenko, Amane, Yeonwoo are good alternatives as well.