brozo: In M&M7 it is a more worthwhile investment but hardly cheap. In my last party through (Sorceror, Sorceror, Druid, Cleric) my "lock picker" was the Cleric who loaded up on Disarm magic items and I had an NPC that boosted the skill early on lots of chests went boom which is why the Perception skill was useful. The problem is Telekinesis is a Grand Master level Earth spell that only the Druid can attain. Works really well once you have it though.
There's a lot wrong here.
Factually incorrect information: A MM7 druid can't learn Grand Master Earth. They can't GM any magic; their appeal is that they can Master both Self and Elemental magics, providing a good backup to both a Cleric and a Sorcerer in one character slot. Also, GM Alchemy to make all your own Pure Stat potions, and those potions are quite a bit better than the MM6 versions.
Edit to add: Telekinesis is a Master Earth spell. The Druid can learn Telekinesis, but they can't learn Mass Distortion, which is the GM Earth spell in MM7. In MM6, Telekinesis is the "top" Mind spell, but you only need the magic skill to learn every single spell; you don't need to invest any points in Mind magic at all to be able to cast Telekinesis.
Informational: Most stat bonuses coming from items don't stack; you only get the highest bonus. I think a few relics and artifacts are an exception to this rule, but if you put on a ring of Disarm Trap +5 and another ring of Disarm Trap +8, then your net bonus is Disarm Trap +8. Hirelings will stack with an item bonus, and as I said a couple of relics/artifacts stack, but that's it.
Next, you chose Sorcerer, Sorcerer, Druid, Cleric in MM7. None of them can even learn the Disarm Trap skill. This party can't disarm traps using the skill at all, and it doesn't matter how many skill bonuses you even try to apply because there's nothing to apply those bonuses to. They are also all on the lower end of the hp scale.
Knowing your party composition, I really don't know what you were expecting. Yeah, traps are going to be your party's bane unless and until you can use Telekinesis to open chests from a distance. Perception (which all of them can only take to Expert level) is indeed going to do more for you in this party than Disarm Trap will.
In MM7 you need a Thief, or at least an Evil Monk to reliably deal with traps. If you're desperate, then a Good Monk, an Archer, or even a Ranger would be able to take a really good Disarm Trap item and handle many traps by reaching Expert.
OP's party is in MM6, where anyone can Master the skill if they can learn the skill at all. Their Knight can get a 21 disarm value with Master, compared to your zero disarm value with being unable to learn the skill. I definitely still don't recommend bothering with Perception with more than one character in OP's party. Incidentally, the Knight should also be handling Perception for them, in my opinion.
For your MM7 party, Perception is indeed the way to go, except I probably wouldn't bother. Early on, skill points are too precious to spend on a chance to avoid trap damage. Later, you have other means of dealing with trap damage, so it still isn't worth the points. The investiture to get a reliable damage dodge is simply far too high because they are stuck with only the Expert level multiplier. You took a party of low hp casters. Despair over your lack of trap disarming while you gleefully nuke monsters with silly amounts of spell damage.