The Almohads have a killer combo for this tactic: Murrabitin infantry and Muwahid foot: the Muwahids have good enough stats to survive for a while, they will recieve a rank bonus (of one rank, but still ) and if they accidently end up with a javelin in their back, they are easy to replace.
IMHO this is about the most deadly line up you can field against heavily armoured enemies. So effective its almost boring. Shame the AI never uses it.