Well, depends.
Arssartuts are very, very tough with a nice blessing. So tough that they'll often force your opponent to bring artillery counters to them (they'll tear up most SCs and troops). Twist fate helps a whole lot against many of the first choices for dealing with ultra-heavy infantry - gifts from heaven, banefire, leech, thunderstrike, etc. You can certainly make do without twist fate, but it pulls its weight through the whole game.