It's pretty simple; You play attrition, a game which both of the mentioned faction are historically bad at.
While it is true that Legion/Circle will outspeed and get the Alpha on you basically always, they are paying a lot more for this than you do. You can almost afford two crusaders for the price of one of their beaters. Which means if you let one of them die, the other can counter attack and smash the attacker into bits.
3 Focus is plenty with a choir chanting Battle, especially since the fast stuff (angels and wolves) rely on DEF to survive and can't take much of a beating. You actually shouldn't have a problem with killing, between Tristan's Feat and Manifest Destiny.
One thing to keep in mind against Circle, is that their most effective way of nuking a model from existence is based on the Primal Animus. However, this comes at a huge disadvantage, because the model Primal was used on effectively has to skip a turn, giving you effectively two turns to get rid of it.
Against Legion, it's very possible that your heavy can survive a charge, under the right amount of circumstances. A jack with the Inviolable Resolve spell might be able to survive an Angelius charge on a box or two, giving you an opportunity to heal it up with Tristan.
Lastly, you as a Menoth player have access to one of the most obnoxious models in the game; The Vassal of Menoth. Just hand out Enliven to your bait-jacks and they will have to take one boosted charge attack and a boosted free strike, but afterwards, your opponent's can opener stands around without anything to do. And if they try to shoot enliven off of you? Either walk backwards and out of range for a charge or forwards and block off a model or two. Enliven is really, really good.