National summons are consistently worthwhile? I think they're generally less awful that regular summons, but still less than a third of them are actually any good. Again, consider stuff like jaguar toads, spectral infantry, rubbish mass animal summons (pack of wolves springs to mind), demons of heavenly fire etc.
Blood summons are incredible. However, national troops can often take most enemies, with the right mage support. (Think massive buffs and battlefield wide enchantments)
Most other summons are only really good for SC/Thug chassis and magical diversification