I did a "quickie" build in Vordans based on the Wizard/EK/Assassin..
A few things to note:
1. Hitting the level increase to 30 - provided only 28 levels for a Yuan-ti (..though it may be possible to gain more levels just on the basis of additional exp. points).
2. Death Attack's paralysis was up to a DC 30 (native), which is pretty good - perhaps even serviceable in Battle of the Builds (with a high Intelligence boosting item).
3. The additional damage wasn't that great, it wasn't bad - but it wasn't good. Scoring an average of 14 per hit with it raised to 19 with Tenser's. By contrast - a critical with Tenser's averaged more than double (i.e. 44). (..and yes, Tenser's does work with everything.

)
4. Base (and bonus) Attack numbers were good, but not nearly good enough for even average AC builds in "Battle of the Builds". Pretty much the equivalent of a base-line medium BAB. Buffed you could take this up to a medium BAB class with good dexterity levels, weapon finesse, and with an excellent enhancement modifier to the weapon (..i.e. - in the mid 30's). Lower 40's with a high Dexterity enhancing item (and of course having the feat Weapon Finesse).
5. Many of the tougher *monsters* cannot be Sneak Attacked.

, Its not just undead, Dragons can't be Sneak Attacked (..or at least the red one I tried it out on). Of course most humanoids CAN be - so it isn't all bad.
6. You do get access to 9th level spells with this build.

But only toward the end of it.
7. You don't get access to HIPS until level 20.
8. There are LOTS of skill points to distribute.

But you need Able Learner to take advantage of it.
9. Craft Potion is useless - it works exactly like scribe scroll. But you aren't wasting a feat here either.
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All-in-all its a serviceable build, but really only when starting into epic levels.
It *is* however the ONLY *efficient* and effective means for a *quality* Assassin *class* character.
Another high Intelligence build could employ Swashbuckler, Assassin, Dualist, BUT it really isn't getting full *value* for its monumental intelligence. What it *will* get though is a higher BAB, but it sure will be useless against a lot of opponents - at least on the basis of Sneak Attack or Intelligence Damage modifiers alone. Add-in Trap setting however and you can probably "equalize" the build for most opponents.