[Shovah32]

I agree, most builds can fit some sort of anti bless rush into their strategy but it dosnt always work, another reason van/hel have such good bless rushes is that they can raid en mass very well, with good stealth and glamour they can make your capitol the first province they hit (this could be with 50+ f9w9 sacreds you never knew existed), keeping only a few sacreds with a big screen of underpriced glamoured units for defence (hel has an advantage here since flying sacreds lets them keep less back with the same response time).

If the enemy see's you building up defences along your border he can sneak past and hit everything else, if you start building defences from the inside out then he can simply take your outer provinces and get more income to make even more sacreds. Finally, if you build both at the same time either you wont have enough defences anywhere and will be open for attack or else you will have enough defence to last a while but will be lacking in some other area (such as research).