1) On Chansey: absolutely not. In general increasing HPs is better than increasing defenses to increase bulk, for a whole mathematical reason that I don't feel like explaining right now. But yeah, if you have time, grab a pencil and a paper, check out the Gen 6 damage formula on Bulbapedia, and try and do some math: you'll see that in general, the more HP the merrier.
2) On Ferro: I might try the split set you suggest, but honestly, I am already content with the purely Physical set I use because in 98% of situations I use it to tank physical hits: if a Special Attacker appears, I generally switch to Chansey immediately.
3) On Excadrill: I personally prefer to have HP maxed out on Excadrill for the reasons stated above: this being said, while I generally like to hit hard with Excadrill when it is not attacking, you do have a point in regard of giving it more bulk to help it stay alive longer and spin better. I'll mess around and see how I can rearrange the EVs to factor in this suggestion.
4) On Rotom-W: I think it's a matter of personal preference. The set you suggest is better to exploit Pain Split and to act specifically as a wall, while the set I use is better to make use of Trick. I just happen to like Trick a lot. Do keep in mind that this team lacks a Taunter, so Trick is vital to cripple those Ferrothorns and Chanseys that keep switching into Rotom-W, and that would otherwise be free to do their job, as I have no other way of stopping them.
5) On Charizard: absolutely not. Charizard is there for one reason and one reason only: step in after a companion has fallen, set up ONE Dragon Dance, and push for game. It is NOT supposed to take hits, I have NEVER used it to take ANY hits (except maybe 4x resisted ones, which won't hurt anyway), and honestly, the day I start using Set-Up sweepers to take hits will be the day I stop playing Semi-stall altogether... Charizard doesn't need to recover, nor to have any bulk: when he attacks, at the end of the turn either the opponent is dead or he is. It's that simple. And it is the duty of the other team members to guarantee that he comes out on top. He doesn't need to shrug off Stealth Rocks damage, because it is the duty of the player to make sure Stealth Rocks aren't there at all when it comes in. And most certainly it is not going to use Dragon Dance twice, unless the opponent is very very stupid. But even when I've faced total noobs, they have always had the decency to send in something with a Rock-type move as soon as they saw Charizard, which means, you guessed it, it's either kill or be killed. And thus, max Atk and max Spe to be sure I am the one killing. As for Outrage+Earthquake canceling the need for Flare Blitz, I have only one word for you: Skarmory (please notice I have no Magnezone in this team). And Skarmory aside, EQ is not STAB and is not boosted by Tough Claws, so chances are it will miss important kills on stuff like Ferrothorn (which in return can cripple Zard with T-wave), Venusaur (which in return can put Zard to sleep), also I have noticed that people tend to immediately send in the likes of Landorus-T and Gliscor as soon as they realize my Zard is the X variant: in a Flare Blitz-less scenario, in order to get past them I'd be forced to lock myself into Outrage (which can spell disaster if the opponent still has a Ferrothorn or a Fairy-type at their disposal) or to flat out switch to something else, which is something that I don't want to do end-game, because chances are I have sacrificed at least one Pokemon to find an opening for Zard to come in, and I won't get another such occasion... So yeah, the only thing you are right about are the 4 random EVs in HP (moved those to SpDef to make sure HP has a odd number).