I've got an idea! Yes, I don't have many. How about filling your Assassin skillbar with just lead attacks? No more problems with the chain being broken! Since leads don't require a previous attack and I'm sure there are more than enough lead attacks to fill at least 5 slots. You can just keep clicking down the line and each one will fire off without regard to the previous attack.
Or maybe you can have just lead and followup attacks. It would be like using 1-2 combos instead of a full 4-5 juggling combo attack.