Fey Warlock has a level 2 utility power(encounter) that allows you to teleport 3. It's Pact Boon allows you to teleport 3 whenever a curse victim hits 0 HP or lower. A feat can make this teleport 5, I believe. It also has a level three encounter power which allows you to teleport, damage those adjacent to your departure point, immobilizing all of those damage(save ends)
So, by level three you could have 3 different methods of teleport, with the Eladrin ability granting a 4th, I believe. Sounds pretty BAMFtastic. I've no access to DDI, so I've no idea what the assassin is capable of, but if it adds MORE teleportation, sounds like the perfect hybrid for such a thing.
Also, the Fey Warlock At will makes you invisible to your victim until your next turn... which could be 'sorta' like teleporting, since if you get any chance to move during that time, it'd seem to your opponent that you just teleported.
Just for fun I made this BAMFtastic hybrid, since I have a DDI subscription:
====== Created Using Wizards of the Coast D&D Character Builder ======
Nightcrawler, level 9
Eladrin, Warlock|Avenger
Eldritch Pact (Hybrid): Fey Pact (Hybrid)
Hybrid Warlock: Hybrid Warlock Reflex
Hybrid Avenger: Hybrid Avenger Fortitude
Hybrid Talent: Armor of Faith
FINAL ABILITY SCORES
Str 8, Con 10, Dex 17, Int 17, Wis 17, Cha 17.
STARTING ABILITY SCORES
Str 8, Con 10, Dex 14, Int 14, Wis 16, Cha 16.
AC: 22 Fort: 15 Reflex: 18 Will: 18
HP: 63 Surges: 6 Surge Value: 15
TRAINED SKILLS
Acrobatics +12, Athletics +8, Perception +12, Stealth +12
UNTRAINED SKILLS
Arcana +9, Bluff +7, Diplomacy +7, Dungeoneering +7, Endurance +4, Heal +7, History +9, Insight +7, Intimidate +7, Nature +7, Religion +7, Streetwise +7, Thievery +7
FEATS
Level 1: Hybrid Talent
Level 2: Improved Misty Step
Level 4: Improved Armor of Faith
Level 6: Frost Step
Level 8: Feyborn Pursuer
POWERS
Hybrid Avenger at-will 1: Bond of Pursuit
Hybrid Warlock at-will 1: Eyebite
Hybrid encounter 1: Angelic Alacrity
Hybrid daily 1: Oath of the Final Duel
Hybrid utility 2: Ethereal Stride
Hybrid encounter 3: Otherwind Stride
Hybrid daily 5: Forceful Assault
Hybrid utility 6: Step of Fate
Hybrid encounter 7: Blade Step
Hybrid daily 9: Summons of Khirad
ITEMS
Rod of the Feywild +2, Vigorous Resolve Vestments Cloth Armor (Basic Clothing) +1, Mithrendain Steel Longsword +2
(As far as Ability scores, our DM allows us an extra 6 points to distribute as desired, so the abilities aren't strictly "legal". When
teleportation wasn't included in a power's description, I chose
shift effects, which could be interpreted as short-distance BAMFs. I'm sure there are even more optimal choices for powers and magic items--and even Nightcrawler's DEX seems a bit low--but I haven't slept in 36 hours so I'm a little loopy. When I'm more awake I might revisit this build, adjusting his Ability scores and magic items a bit futher.)