I'm afraid there are few weaknesses, actually... The system is much easier than it seems: most glyphs do one and the same damage per drop of colour, and what differs is how suitable its way of work is to take down particular enemy. Though, exploding boulders do a bit more damage, than all these usual variations of tumbleweed with lympha inside:).
My favorites for the beginning of the game are Wasp and Sleeper, as they usually pop near the beginning, and may be used against almost all enemies. Owl or Tumbleweed are a good choice for the fight with Warden (and Juggler too). It's hard to take him down with Wasp (because he moves constantly).
Some tricks
- S-shaped glyph seems to deal a good damage at a certain distance, i.e. it consists of a number of "damaging points" that move away from the player. If your get many of the point hitting the target, the damage may be huge. However, they don't do much harm NEAR you.
- when you use Magnet, you can punch the "gravity ball" so that it hits the enemy. If the objects collected by magnet do harm, the brother will be damaged.
- Whaler becomes stronger and faster with each head he gets, but his defense becomes weaker at the same time. The fight is lost if he has 4 head, but 3 heads will let you defeat him with the least lympha expenditure.
- Ironclad has just the most hitpoints. That's why he is tough to kill. Ritual is quite effective to deal with all his small portable cannons at once. Magnet can also serve this purpose: just collect all the cannons in one corner of the level, and don't go anywhere near.
- Patriarch is not only quite an average Brother, characteristics-wise, but has an additional way to kill him with even more ease. The boulders lying all around the level can be set on him. First paint over the boulder with a drop of colour, and then use a drop of colour on the Patriarch.
- use Shell with Triumphator.
- Pit's drills can hardly ever reach you if you quickly get to the opposite side of the arena after the brother springs out the ground. Note also that each time he tries to appear as close to your position as possible.