Traits are being reworked and none of this may matter come EA or soon after EA starts but I will try to answer your questions.
Magic resist is overall the easiest and best choice for most characters as it does remove everything you mentioned. Charismatic is a good choice for charm classes if you plan to charm as many charmers claim the charisma snapshots when you cast charm and allows for the charm to last longer. This probably needs further testing but that is the information I have from several level 60 enchanters that charmed a lot in Alpha and Beta.
As for defender vs channeling I would highly recommend defender for anyone except tanks. The reason for this is you always want defense to be as high as possible but you do not want to be hit often. Channeler is a waste of a trait in my opinion because you will easily max this skill every level with any class that casts spells. Every single cast of any spell will have a chance to increase channeling.
None of those traits increase the max you can have in a skill. They only increase the rate you gain the skill
