Light armor all the way. Reason:
When you switch to cleric rod, while wearing light armor, you get these from the light armor cleric passive...
- Magical defence power 212 Increase;
- Physical defence power 117 Increase;
And, when you use Body Deity and Soul Deity on yourself, you get an extra...
- Physical defence power 176 Increase;
- Magical defence power 318 Increase. (these last only while using cleric rod, and you can use these 2 buffs don't matter what your armor is)
If you are using light armor + cleric rod and are buffed, you get an extra 530 mag def and 293 phy def, not forgetting you can wear a shield (lets use a lvl 85+5 shield with nothing else added: 153.4 phy def and 245.9 mag def ) achieving then a total of 775.9 extra mag def and 446.4 extra phy def. While using light armor + cleric rod you can easily tank, heal yourself and do anything else you might need from cleric.