The only d4 die the Alchemist has is Charisma. The only d12 die the goblin has is Constitution. They have a d8 and d10 Dexterity respectively. Also, Underwater Spike Trap? I'm thinking you mean Drowning Spikes Trap?
First off, that's an Adventure 1 bane, so if you were playing a demo, you shouldn't have seen it. You should never jump into Adventure 1 for a demo and I'd highly recommend not jumping into Adventure 1 ever without experienced characters (play the five introductory scenarios first to get some upgrades.
Second, it has a Dexterity/Disable 7 to defeat it initially, which the Alchemist shouldn't have had too much trouble with if he got a little help since he has a d8+2 in the check naturally. Then, the DC 9 check is Dexterity/Acrobatics/Strength. Most characters, if they're unlucky enough to fall, should have a die that is least a d6 between those abilities/skills unless they're really, really weak. The Oracle is the only character in the base set and add-on deck that has a d4 in both Dexterity and Strength, so maybe you're misremembering the situation and that's who actually got caught in the trap?
And lastly, traps suck and they should suck, just as they should in the RPG. Typically, taking care of traps is not a team effort.
There is a lot of character interaction in the game, but most of it is not as obvious as things like helping a friend out of a trap. Most of it deals with working together to develop a strategy to reach your goal.