You can, of course, use the English language where Russian fails to convey certain concepts, but I suspect that "piercing crossbowmen," "long-orange archers," and "firebite warlords" don't sound quite as good.

It's an excellent name, but we already have Storm Titans, and I don't like repetitions.

Possibly. But it seems to me that this is gilding the lily.

Well, that's essentially a description of the unit's "character." I'm open to suggestions.

A poisoner is not necessarily an assassin (and more often than not, it isn't), and an assassin is not necessarily specialized in poisoning. But an assassin-killer is gilding the lily (not every killer is an assassin, but every assassin is a killer).

The entire essence of the unit shouldn't be derived from the name. The purpose of the name is to maintain an association with it. A player who has at least once become familiar with gladiators and their abilities will always understand which unit is being discussed when they hear "gladiator-interceptor."