this is part of the reason RE:Start is in such a bad place. With the mix of mechanics, certain things are far too confusing.
With you not wanting Int in your build, using both Holy or Grand Cross is a bad idea.
Holy Cross simply because you will have barely any Int to cast it with, also I'm looking at the skill and it says nothing about spears. (Seperately, there are very few One-Handed Spears, which is what you would need to use in order to wield a Shield of any kind)
And Grand Cross because is requires Str and Int to be truly effective.
http://ratemyserver....&small=1&back=1
the above link is, as far as I know, the most accurate and up to date info on Grand Cross and how it works.