TRAPMAKING:
It's a great idea, but suffers too many technical and resource problems to be a viable addition to any playstyle right now. I've been testing them on my Rogue2/Wizzy18 Drow PaleTrapper, and I have found the following:
*My
Crafted Trap DCs are very high, but this is meaningless if the traps never trigger or land properly. Mobs have a habit of slightly skirting the trap, even if they are chasing you with full aggro multiple times across the trapped area. And I don't mean 5-10 feet away, they go right up to the trap, do a little sidestep jig and run by, not triggering them at all. Very frustrating. I am an excellent kiter, but it is ridiculous how close I have to drag a group to a trap before it will do anything. I would suggest increasing the trap activation radius by quite a bit, unless mob AIs can be adjusted to not basically make a "running evasion maneuver" that they should really NOT be able to do while chasing a jumping, hasted, tumbling target at top speeds. They also have a tendency to run *around* a freshly-burst Web or Grease Crafted Trap area, more than their AI should allow.
*Another idea to help make Crafted Traps viable would be to add the ability to
*remotely detonate* a placed trap, so that the user could time the explosion or spell burst effect. (And the tech is already in the game from the Blockade Buster quest in Lordsmarch plaza.) This would allow a skilled user to get the most out of emplaced Crafted Traps, and fit better with the theme of a Mechanic who uses Magical Tech to DPS and/or CC. Without this ability, there is a ridiculous amount of kiting needed to get mobs near a Trap Killzone. It would add a layer of tactical gameplay that would appeal to many players who don't want to just do "max DPS" as their only playstyle. And it would make DDO more fun!

Traps are a unique feature of DDO, and the devs could really emphasize this with some changes to Crafted Traps to make them more viable.
*MAGICAL trap parts are currently too rare to cost as much as the other trapbuilding recipes. They don't drop often enough from a reliable source of Spellwards to be farmable. So a user's supply of Web, Grease, Ottos and other traps becomes an always-shrinking stockpile taking much scrounging to keep up on. In fact, the elemental trapmaking costs are also a bit high, especially if you are going to make Crafted Traps a part of your routine. Melle do not need to make and consume any doohickeys to do Sword DPS, and the Ranged and Spell Attack components (arrows and spell components) are obtained inexpensively from a variety of sources. I would suggest cutting the costs of the first component in each trap recipe (Magical or Elemental trap parts) at least in half. Mechanical trap parts and the Elemental Essences are readily available and are fine for costs.
*I agree with many previous posters that the
AoE of a triggered Magical Trap is too small right now. Making stuff like Deep Slumber or Slow traps is pointless, as they never land. Often the mob triggers it in a run-across and the effect hits right after it leaves the area. They don't even get a save, it just doesn't hit. Currently this is a dead-end area of Crafted Trapmaking and needs to be addressed to be playable.
*The
damage of the Elemental Traps is also too low. One idea would be to make Crafted Elemental Traps whose DPS output is based on the SPELLPOWER of the one that crafted them. So each trap would have a quality rating, adding that spellpower to the elemental damage when the traps goes off (DCs would still be based on the Disable Device skill of the one setting it). It could easily cost a higher and higher amount of elemental trap parts to "infuse" a trap with a higher Spellpower Rating, and certainly should have minimum Disable Device skill ratings to even place such traps (so low-level characters could not purchase/craft very high level traps and use them in lowbie dungeons). I like this idea, because it addresses the usable DPS issue of Epic-level traps, while also creating a new economy within the game for interdependent Crafted Trap Parts Farmers, Trapmakers and the skilled Trappers who would actually use them as a reliable source of DPS. I know I'd get back into the Auction House Game of DDO again to both sell and buy these items, or the components used in making them. And it would give some new activity to the game, as people would have a reason to create skilled Trappers and Trapmakers, farm trapped dungeons for parts and spend some time in this Crafting Mini-game!
Just a few ideas on how this unique aspect of DDO can be improved. I hope the devs give it more attention, as I really enjoy this playstyle and hope it becomes viable for Epic play in the future. I play an Engineer in GW2 and have a lot of fun with it, as the class is designed to use Magical Technology for DPS and Crowd Control (and Healing in that game), making it a flexible and fun addition to the mix. The Eberron campaign setting that DDO is set in has a huge backstory of using magical tech and it would be great to have this reflected in the actual DDO game mechanics as well.
<See? Ghallanda Downtime had a positive impact today, time to post this....> =P