I've had some thoughts on this topic for awhile. In my opinion, being fast doesn't really help ranged creatures, and it should. Mobile archers exist(ed) both in real life and in many popular forms of media.
Instead of changing the Johktari Beastmaster or her bow, I think it would be more beneficial to add a few new rules. Here are the possibilities I've thought up:
1. Biggest Buff to Ranged Units:
Instead of taking a full-action ranged attack, a creature may instead move one space and perform the listed full-action ranged attack as a quick-action. The attack loses 1 maximum range, 2 dice, and 4 from the effect die roll (if any). If the creature possesses the fast trait, it may make one free movement without incurring this attack penalty, and may move up to 2 spaces in total before declaring an attack.
2. Medium Buff:
If a creature possesses the fast trait, instead of taking a full-action ranged attack, a creature may instead move one space and perform the listed full-action ranged attack as a quick-action.
3. Minor Buff:
If a creature possesses the fast trait, instead of taking a full-action ranged attack, a creature may instead move one space and perform the listed full-action ranged attack as a quick-action. The attack loses 1 maximum range, 2 dice, and 4 from the effect die.
Option 1 (which is probably overpowered) makes ranged units just as mobile as melee ones. Option 2 allows the fast trait to benefit ranged troops just as much as melee ones. Option 3 basically just allows for occasionally better positioning and mobility at the cost of effectiveness. Regardless of what happens, the Johktari Beastmaster really needs more synergy between her traits and abilities.
For those wondering, I came up with the attack penalties by picturing half-drawn bows (less distance, less impact, but faster).