Euro may be the defensive faction out of the allied ones, but they are also the balanced faction in gameplay. They do have plenty of defensive means (snipers, thor deploy), but that doesnt mean *everything* has to be.
In chinas case their stuff i really slow allround except for dragonflies, but they offset this glaring weakpoint by exceptional armor and emp usage. Euro has neither of those, they have more specialized units that cover each others weakness quite well. Ergo a faster unit with good range actually fits into their theme imo. The prism can move out to strike with range advantage and afterwards quickly withdraw behind the defensive lines of charons, mirages, snipers and thors. Also keep in mind that they already have a slow, tough siege unit: he's called Siegfried. Sure, he's more of a mobile army deleter than base razer, but he is the tough, defensive arty unit you seemingly want in euros arsenal.
Oh I beg to differ with Siegfried, I never use him ever since I found out what he does. Just doesn't fit my play style. But each to theirbown of course.