I'd say that Assassin is a good choice in the linked build less because you're building around the bonus and more because the drawback doesn't hurt you much. You're really in Rogue for Sneak Attack, Deathblows, and cheap Full Attack abilities. Without making any special efforts, Assassin will benefit you often enough to be better than a base-class Rogue. And, if you aren't interested in taking on micromanagement and risk associated with the Streetfighter playstyle that Jayd describes above, that's probably more than the other Rogue subclasses offer. (That said, a Trickster giving up a little SA damage for debuffing utility is a nice tradeoff. Being ranged, you won't get much out of the PL 2-4 abilities, but the rest can be fun.)
IMO, Helwalker is too natural a fit. Makes good use of the feedback damage, the MIG bonus helps a lot, and the disadvantage is substantially mitigated by a ranged build. I'd consider that a lock for half a mulitclass.
If you don't want the other half to be a Rogue, you're probably giving up some overall damage, but what you get in return can make up for it.
Ranger gets you Driving Flight, a pet, and a suite of ACC-enhancers. A Ghost Heart make a neat thematic pairing with a Helwalker, too. (Although note that the Ghostheart pet isn't compatible with Dichotomous Soul, due to the summons cap.)
Devoted adds even more PEN, easy access to Intuitive, and a damage boost on Crit. Not sure how useful extra PEN is at that point-- between Desctructive Channeling, Thunderous Blows, Scepters being dual-damage, and the Ring of the Marksman, I suspect you'll be pretty solidly in the PEN-but-not-OverPEN category for Hits and at or near Overpen on Crits, even without the Devoted boost. (Aside: does the Scepter modal stack with Tenacious?) There is a cheap full attack (Penetrating Strike), but it's not as good as the Rogue options.
Paladin lacks great DAM ACC or PEN boosts, but but it does have an excellent spammable Full Attack, and contributes lots more party-support utility than the other options.