While I certainly feel no need to have cost 5 traps, I don't think they are impossible.
Some triggers are pretty certain to occur; the iffy part is simply when and how. I never fear my lost at sea trap will never be triggered; I fear that it might be triggered by something like horde of animals. And even the "swinginess" of what triggers it is mitigated from my opponents viewpoint by knowledge a trap is there and a good chance of guessing which trap. From my point of view, it is mitigated by the fact that it at least forces my opponent into playing cards with different timing than would otherwise be planned.
And I can think of at least a couple of traps that might be worth at least 5 power points. For example:
1. Traitor: the next card played switches sides, played in a random empty location or on a random legal target.
2. Pain mirror: the next damage you would take is instead reflected onto your opponent.
The point is that there are several very good spells.
I cannot say the same for Auras, Items and Traps.
On top of that I think most of decks win the game through a combo of minions and spells, while the other cards are just used to change the environment to gain a specific advantage but none of them is able to let the player win as stand alone card.
I would like to see more Auras, Items and Traps (i.e. opponent damages) which can lead you to the victory without other cards.
I think some underused auras and items may still need a slight cost reduction to make them more appealing and to get players away from minion/spell only type decks
There will be larger auras coming with Ice.They are the master of auras and have many ways of controlling the game with the them.
I think the whole point of Auras Items and Traps is to facilitate rather than directly damage to win right? :)
And I'd be disappointed if my opponent beat me just because they had some uber-trap I couldn't do anything about - I like to be beaten by their card combinations and placement/timing skill, which you yourself have demonstrated a number of times