The tapus are good, but not broken. Otaku laid it out pretty nicely. Lele is easily the best out of the four because it's an S-tier support Pokemon with a great attack. There is little opportunity cost to using it.
Re the rotation: You're deluding yourself if you think the rotation is going to be EVO-on. The only reason the emergency rotation happened is because Sableye donk decks were busted under the new Black and White rules. Being able to play Trainers, as well as attack, on your first turn (as well as being guaranteed to go first thanks to Overconfident) is what forced TPCI to act. The format would have devolved into play Sableye donk or lose.
Sets are almost always always cut in easily definable blocks where the earliest set in the rotation is also the first set introducing a new mechanic or game:
00-01: Dark Pokemon (Rocket-on, 4 sets removed)
02-03: Gen 1 rotates out (Genesis-on, 3 sets removed))
03-04: e-Card series (Expedition-on, 5 sets removed)
04-05: Gen 2 rotates out (RS-on, 3 sets removed)
05-06: First set without Dot-Code data strips on cards (HL-on, 4 sets removed)
06-07: an exception here, as Pokemon-* were introduced one set prior but that would only yield a two-set rotation (DX-on, 3 sets removed)
07-08: Delta Species (HP-on, 5 sets removed)
08-09: Gen 3 rotates out (DP-on, 4 sets removed)
09-10: no rotation
10-11: no obvious pattern here, but four sets were lost, making this fall in the normal 3-5 set spread (MD-on, 4 sets removed)
11-12: Platinum sets rotate out to remove Sableye SF and the SP engine from Standard (HGSS-on, aka emergency rotation, 7 sets removed)
12-13: Gen 4 rotates out (BW-on, 5 sets removed)
13-14: Pokemon-EX (NXD-on, 3 sets removed)
14-15: First BW2 set, also ACE SPECs (BCR-on, 3 sets removed)
15-16: Gen 5 rotates out (XY-on, 5 sets removed)
16-17: Ancient Traits (PRC-on, 4 sets removed)
Following this pattern, it stands to reason that the next rotations should be
17-18: Pokemon BREAK (BKT-on, 3 sets removed)
18-19: Gen 6 rotates out (SM-on, 5 sets removed)
19-20: Some mechanic which will be introduced in SM4 or SM5
The only time in this game's history when more than five normal sets were rotated out was due to mechanic changes that would have made the game virtually unplayable. In addition to this, before the ban, there were twelve sets in Standard, and that's only because there was no rotation for the 2010 season. Had they shifted to MD-on in 2010 and then done something like Platinum-on in 2011 (first Platinum set, 3 sets removed), the shift to HGSS-on would only have removed four sets, well within this long-established pattern.
Should Sableye prove to make the game unfun, all they have to do is move the rotation up a couple months. BKT-on would remove both Forest of Giant Plants and Vileplume from Standard, thus eliminating the core problem without resorting to gutting the format. I could see them doing it for Worlds, along with making SM3 legal, just to shake things up.
As an aside, I'm actually a little surprised that they didn't bring back the additive weakness modifiers from gen 4. It would have made non-GX Pokemon a lot more viable since one-shotting them with a type they're weak to would happen much less often. I wouldn't have minded seeing it back.