Eh, you can't count on the wildshape restriction to shapes you've seen to be meaningful. Any of the forms could appear at 1st or 2nd level (they're CR 1), any of the forms could easily be witnessed through appropriate scouting (okay, guys, welcome to level 2. We're taking a quick trip up this trail to see an animal), or may be covered by background.
For example, of the two druid players I've seen, _both_ had a background that they were raised by animals. One by tigers, one by wolves. At that point, the limitation is a hit to versatility but not a hit to power, and becomes more punitive than effective in limitation.
Yes, but this is DM dependent. If the DM says (possibly after a dice roll to determine it) "No, you haven't encountered a giant spider yet", then that's that. I could also see a DM putting the kibosh on being raised by tigers, especially if the campaign world starts someplace where they might not exist (e.g. HotDQ on the Sword Coast).