The ranks numbers are not high enough unless you want rogues and monks to get improved evasion long before they could gain it as a class ability.
Evasion: Dodge, Mobility, Tumble 5 ranks, Dex 13+
Improved Evasion: Dodge, Mobility, Evasion, Tumble 13 ranks, Dex 15+
Uncanny Dodge: Alertness...