Since Avatar of the Jaguar has overall better defensive Traits and greater Damage total, it makes sense to move him first, moving Stalker into position at the next opportunity.
With high value and Trumped Agility Traits, with the Super Duo bonus they are ideal for weathering the storm against ranged attackers targeting against Agility. Use them in tandem to take out high Damage-output ranged attackers, freeing up the rest of your Team to go about their business.
Alternatively, they can be very useful against high Defense models like Iron Train. Build up by stacking a Prowl Token onto Iron Train. This can and should be done in an earlier Round to what follows. The plan is that Avatar of the Jaguar and Stalker weaken Iron Train enough for him to be heavily Damaged in a single round (plus subsequent Effects Phase).
Follow up with a Charge* and Rip from Avatar of the Jaguar to maximise chances of success - there is no guarantee and this is a risky option, but with Quadruped Skill and Charge* Avatar of the Jaguar has a net +1 over Iron Train in Trait differential before any Power-Ups are applied. If successful follow up as soon as possible within the same Round with Stalker also using Rip and Charge* - if Avatar of the Jaguar succeeded and equal Trump Rolls were expended, then Stalker should be attacking with effective Strength 7 against a Defense of 5. Assuming that Avatar of the Jaguar and Stalker have optimum remaining AP Allowance, this allows for anything up to 2 Strikes from Avatar of the Jaguar and another from Stalker - combine Prowl* with Stalker's Strike to maximise effect. These Strikes will be against Iron Train's modified Defense of 4 and any AP he expends to defend with Power-Ups limits return attacks. While this will likely only shave a few Damage from Iron Train, it then leaves the model open for a well placed attack within the same Round against either Defense or Agility from another model on your Team.