There is dialog, not a ton but it's there.
Hmm, yes, there is some. Up to the point I played at least, it was not a major gameplay element, and I don't get the feeling it will be.
Exactly how far into this game have you played?
I believe I just started chapter nine (fort Frolic) so about half way? I know that there are tasks, but they don't strike me as vastly different from the level goals in any other shooter. There certainly didn't seem to be host of quests to choose from so that it would qualify for a typical main-quest / side- quest structure.
It most certainly does have open environments, but I didn't realize that was necessary to qualify it as a hybrid. It's not the least linear game I've ever played, but it's certainly not the most either.
Well, from a gameplay perspective it is a "clear / traverse the level" experience to me, occasional backtracking doesn't change that. It is not a requirement, but e.g. DeusEx and System Schok seemed to allow more different ways to navigate the maps, and exploring seemed to be more important (this is of course subjective, but I remember scouting out the levels in Deus Ex for a long time before I actually took action - not so in Bioshock, I am basically drawn from confrontation to confrontation, encounter to encounter).
What games are you comparing it to that makes you so sure it can't be called a hybrid? Perhaps you could give some examples.
Deus Ex and System Shock are the principal RPG/shooter hybrids in my mind, (Outcast is an example for an action adventure / RPG hybrid to me. Spellforce the quintessential RTS/RPG hybrid).
The main point is, in both DeusEx and SS you got clear options for character progression, the mechanics supported specialization into different character builds (although to an extent allowing jack of all trades builds). And at least in DeusEx, dialogue had a little more weight. Ultimately it is only my opinion of course, but the experience I am having with Bioshock is much more like Half-Life 2 then like SS or DX. Mind you, I am not dissing the game at all, I like it for what it is, and definitely mean to finish it.