Is finding Heavy Armor with Caster stats as easy as with Cloth?

Mods are largely based on which attribute(s) an armour piece is aligned with.

Most caster type mods are probably associated with int, meaning they'll occur (or are more likely to occur) on int, int/str and int/dex armour pieces.

Int/Str armour could easily be described as 'heavy', but can get those mods easily due to being int.

If you play a templar, you'll most want Int/Str armour, which can get both int and str mods, and has both armour and energy shield.

If you play a witch, you'll most want pure Int armour, which only has energy shield.