So, the armour of destiny grants a 4+ ward save, and the talisman of protection grants a 6+, do these stack so I get a 3+?
You have to allways choose the best ward save so you do not get parry if you have a wards save that is better or equal but you can chose regeneration if it is a better save. ward save does not stack like armour but you cant reduce it either only take away it with special weapons. Rdead page 44 for war save and 74 for regeneration in the rule book. Dont forget that parry doesnt work if your model has frenzy.
Another useful point to bear in mind is that magic resistance does stack with a ward for magic purposes. So a Obsidian Loadstone in the unit would buff a 5+ Ward to a 2+ against magic!!!!!