wel.. the current system punish multi class heavily.. and here is my idea of solution
1. core ability should not require the previous core ability as prerequisite
2. first three core ability should require 1,2,3 level in the class, fourth require 5 and capstone 10
3. five tier of enhancement should require 1, 1, 1, 5, 10 level in specific class to master.
p.s. not all class are good and viable to multiclass.. and i don't see any reason why multiclass should be equally as pure class... if people spend more time working, planning on the build, it should deserve to be better. one of the reason of why this revamp was introduce is to add more verity possible build. and if mutliclass grant no benefit then people will just go pure, and get board very fast. at least i won't be playing pure build every life...
p.s.2. also in dnd rule prestige do not depend on the level of base class, they may require one or more base class level and other skill,feat requirement. ddo is currently further and further away from dnd.. perhaps do this right for once?