i ahve to say in all the games i have played so far of wich there has been one hell of alot, i cant think of a single time a trooper has been in a position to sheild a shadow from a tank gun.
infantry tend to hold areas such as buildings while for example the shadow is moving down flank to hit an enemy armoured unit, if it carried troops then they tend to deploy into cover with the shaow out of LOS from the enemy, or the shadow being used as block between enemy and themselves.
if your using tactics such as using infantry to protect a shadow can i be the first to play you and put a £100 bet on the table for whos to win. if your army for example was just infantry and a shadow killing the shadow is all well and good but in same turn if you killed all the infantry you just shattered the enemy with ease after all a tank shell can still miss.
the point od most BF-evo games is to shatter the enemy, and thats the most important tactic in the gme, always aim for shatter.