I have also noticed these are very unbalanced between different troop choices for offence.

Yielders Gard is by far the easiest to obtain which gives bonuses to killer offence during an attack.  Next easiest would be Hunters Guard (hero energy spent) and you would just about hit level 2 in this Gard before you got the level 1 Shamans Gard (assuming you spent an equivalent amount of energy which is VERY unlikely given shaman's energy costs more than twice as much gold as the equivalent hero's energy).  The Archers Gard is ridiculously hard to get for the average player until you get close to level 30 palace.

So these Gards clearly favour some troop types over others and are ridiculously out of balance.  Killer > Melee > Siege > Archers

I would like the offer of being able to reset my troop upgrades in Valkyries Citadel (with full return of resources and boosts) if you are going to introduce changes that unbalance the game so much!!!