All right, tried carefully both Trap Shadow and Scratch and there's defenitely something to say on them
Trap's best path is Trap Trickster fo sure: his traps are very good, especially PvP and powering them up really helps. Notes that if the trap has been on the field for at least 3 seconds when you toss another one, the old one explodes for a good 45 damage instead of disappearing. This is obviously most useful in PvP where you can stack this "combo" relentlessly against far away opponents
Feral Instinct path really does'nt give him anything... the swipe combo locks him in place, it does'nt dash into enemies like Free Ranger's, so it's both risky and underwhelming for story and defenetely useless in PvP, using his standard claw attacks and Wow Pow is much better. The claw damage overall does'nt get improved, so it's a useless upgrade. Go with the traps
Shadow's best path is the Kick path: it's not great, but it do improves both the range and damage of the shadow kicks, but not the damage of the "shadow form" and the coming-out of the shadows attack, wich is strange since those are tecnically... Shadow attacks as well
. Per se, shadow kicks are an extra feature on Trap Shadow, but may be useful to some other swapper top that lacks a consistent mid-range attack like Grilla, Free and so forth.
Prowler would like to give you something like Flameslinger and Zone's flame trail, but it's not the same at all... the shadow steps stay on the field for a very, VERY short time, so they're not near as useful at controlling space like the Flame Trails, however, they do tecnically improve the damage you do when going invisible, so it's nice for Story, where enemies stop attacking you when you're invisible, and you can go all out on them. Use this path solely for Story and Arenas, not PVP
As for Scratch, she's actually good on both paths: Ruby is more aggressive. The Jewel Beam does increased damage (17 instead of 15. not much, but the more Crit upgrade also helps) and makes the opponent occasionally flinch, hindering his attacks, while the spinning claw attack is powerful and homes on the enemy (it also aims for the opponent in PvP, it's not a dud like Free's slasher combo), where she can start slicing him. This attack is also hard if not impossible to interrupt once it's charged. This is defenitely a fun path build for offence with a nice tool to use at distance
Shappire on the other hand, is a zoning path: the beam slows the opponent down instead of making him flinch, so they can still attack, but it gives you more time to react and dodge them, while the charged whirlwind generates a big vacuuming tornado in front of you, the whirlwind actually does little damage (9 per hit) but it has a fairly powerful vacuum effect that prevents opponent to either escape or get too close to you. The charge time is very brief so it can be used consistently, combined with the Jewel beam properties and the +10 speed upgrade, this path allows you to keep the opponent where you want, like a...
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... cat playing with the mouse!
She's not broken, but very strong on both paths for different reasons: Ruby is powerful and easy to use, Shappire is mobile and requires some skill