The higher the rally point, the more Troops per Hero can be sent out.
For example a lev 9 rallly point allows just 90k troops.
That can be changed with the use of buffers though.
Corslet: Increase Troops defence for 20% good for 24 hours. Good to use if you are attacking or getting attacked.
War ennsign: Increasse the amount of troops you can send by 25%. Which explains how you can get hit by a wave of troops over 100k. Goodfor just that troop movement. Typically used on the first attack.
Penicillin: Cuts troop loss by up to 30 %. Good for 7 days. Means that you'll have more troops to heal at the rally point.
War Horn: Increase attack power of troops by 20%, good for 24 hours.