Enchantments can be stripped.
Hexes can be removed.
Spirits can be killed.
Spells can be interrupted.
Attacks can miss.
What was the balance of a shout/chant? The recharge time. Yes, shouts and chants are extremely effective- but with the price of a short duration. For example, old incoming would give you a 50% damage reduction 1/5 of the time. While powerful, by timing spikes and such outside of the duration, one could win even with an incoming paragon on the other team.
But the problem is... what happens when the balancing agent is REMOVED from the game? Say, for example, hexes must last their entire duration. They cannot be removed. The hex metagame would go through the roof! The balancing agent has been removed, and now hexes are Godlike. I could go on and on about this, but I think you get the idea.
Here's the problem with shouts and chants. The main balancing agent CAN be removed by the players at will. I am talking about Incoming! chaining, for this example.
Incoming was relatively balanced at a 4 second duration. However...
Incoming affects the ENTIRE party, yourself included.
By using a second incoming, it is as if the duration of incoming just DOUBLED! Sure, at the price of an elite slot, but for something as broken as that, who needs an elite slot?

So as a result, Anet pulled out the hammer and smashed shouts and chants over the head until they lay there dead. This was effective, as chaining Incoming to get 8 seconds with 2 players now would take THREE players to get 9 seconds. But what about people who want to use the skill... well, the way it was supposed to be? They got screwed over by the fact that anet used the hammer to annihilate powerful shouts and chants.
But, in my opinion, there is a much better way. How? Make the balancing agent untamperable. How do you do this? Let me illustrate with Incoming!.
[Old] Incoming!
For 1...4 seconds, all party members within earshot take 50% less damage.
10E 20R
Now watch my idea for how shouts should be handled:
[My] Incoming!
For 20 seconds, all party members have incoming. For the first [1...4] seconds incoming is on each party member, they take 50% less damage.
10E 20R
Now take a look at what I did. Incoming now "lasts" as long as it's recharge (which would be applied to all shouts in my idea). However, the EFFECT only lasts for 1... 4 seconds- the FIRST 1... 4 seconds. So if after that 1... 4 seconds, another paragon casted incoming, it would increase the duration... but this doesn't matter, as once the 1... 4 seconds are up, incoming does NOTHING, and chaining it like that would just increase the time it does nothing for.
Also, for skills that say "Under the effect of a shout or chant", Incoming would only effect that for the 1... 4 seconds because after that, they are no longer under the "effect" of it. It is still on them, however, to prevent it being up for longer than the developers intended.
This fix is a creative way to make it impossible to chain shouts and chants, making them a lot more balanced and more importantly not abusable. Even if this is decided to not be a good idea, I am sure that by revising the shout mechanics, they can become much more balanced...