The ranks for Tumble set at 5 stop a Fighter from getting the Evaions feat until 7th level (Cross-class skill). Adding Skill Focus (Tumble) does nothing, but raising the ranks required to 6 means the Ftr has to wait til 9th level.
This isn't designed to 'stop' anyone. Tumble is the one skill most closely associated with the Evasion ability based on its description. If you're making something previously inaccessable suddenly accessable to others, this is a sensible requirement. Making the feat required Skill Focus makes that feat a little more important now and also is a good choice not just for flavor but to keep the requirement a requirement by not letting classes that get bonus combat feats practically ignore prerequisites. Levels have to be gained to get Evasion as it is, that means training, practice, etc, and if the classes that get it have to gain levels, making classes that don't normally get it spend one of their hard earned feats, well, that's a fair price to pay while not letting those classes wtih the bonus feats suffer because they didn't take a combat based feat.
Putting Improved Evasion at 12 ranks of Tumble means any class without it as a class skill can not get the feat until epic levels (21st level).
That is simply just not true. There are plenty of feats/house rules that would allow any other class to take Tumble as a class skill, and thus meet the requirement way before Epic levels.
Uncanny Dodge: Again, Skill Focus (Spot) does nothing, but Spot ranks at 6 means a Ftr has to wait until 9th level to get this feat. Druids, Rangers, Rogues, and Monks could pick it up at 3rd level (Class skill). Add that you need Spot and Listen at 7 ranks and Alertness (gets both skills in one feat) and Ftrs need to wait til 11th level to get this feat. Drds, Rgrs, and Mnks can get it at 4th level (when Rogues get it as an ability).
How does it do nothing? Uncanny Dodge is an ability that is earned based on the character's senses. Using Spot or Listen are the only two skills based on senses. And I mentioned nothing about using both as requirements. Alternatively means as an alternate; use Spot or Listen, not both. Yes, those classes could pick it up at 3rd, don't forget Barbarian by the way, but that means they would have to spend one of their (1st, 3rd, and/or Human) 2 or 3 only feats to take the required Skill Focus feat
and another feat for the UD feat. This leaves them with only 1 other feat. That's a pretty decent, if not steep, price to pay if someone wants to get that ability that early on.
Again, you are not listing all the prerequisites and that could get dirty for those classes that do get the abilities. What other feats say that several Core Classes cannot take them? If you make it so that there is no advantage to take them (you can't get it earlier) then no one of those classes will take them, and problem is solved without adding unneeded special rules.
I thought I did list all the prerequisites I would use or suggest be used. No other feats say classes cannot take them but these are not feats. These are class abilities that no one else can take right now being made into feats so other classes
can take them--that is the advantage in taking them. And its not about being able to get them before the classes that get them, get them. It's about being able to get them at all since, right now, only those classes that get them, get them.
Spending a feat and putting ranks into a skill that should be developed anyway is hardly a terrible price over having to multiclass 2-4 levels to get Evasion and UD.