Should just get Serker and WD to 1370
You can leave them there for a while and they'll be paying for it soon. You can also skip Yoho on Do Lopangs, but you nevertheless, you should at least resting Chaos Dungeons on Serker at the very least until you have alternative options that could replace them. You can limit WD until 1370 if you're planning to pump the Bard up for the upcoming reset. I'd still recommend both, as they're both close, to 1370. Chaos Dungeon is easy to play and offers decent rewards.
It's prior to the 1415s, imo. Simply take one weekly reset's gold that's in the 1370s, maybe the same week or week, if you've got raw gold to hone and then go through the Pala and then (might require a week or so) Sorc until 1415. You could also matchmake Argos from the 1370s for some lost ark gold, too since P3 buses aren't as interesting for alts that aren't further honed. I'd suggest keeping the Sorc at 1415 to get Oreha gold until you've the money to upgrade her up a bit.
I'd suggest that the primary problem for you long-term isn't even the fact that you're catching alternative players (or in the singular case one, the Striker, perhaps?) but rather the reality that you're starved for gold and some of your classes cost a lot in terms of gearing. WD and Striker each have a reason to need every tripod and gem they can get, but their best moment to shine is the relic sets. Igniter isn't cheap either to turn into the relic jewelry. All of their engravings look like other places, so I'm not sure whether you've got any famous books you've read or have a roster of characters, but it isn't easy to fill by a single choice (unless there's Grudge).
It might be difficult to set them properly by 1415 and keep this in mind. It's not really worth it trying to improve your skills until 1415, but not to get caught up in Valtan gatherings. This is something to think about to keep in mind for Sorc coming up, after which you can move to WD and then your Striker (or any other 6th alt that you'd like to achieve 1415). I'd suggest hone each 15ilvl at a stretch and work at it slowly. The new Chaos Dungeons on 1385/1400 help mostly with shards, meaning you don't need to start an event or purchase all of them. That's specifically for Bard and WD specifically. (Though Bard will find a party in any way.)
1370s are a great source of gold. It's like 3k/week. Therefore, just keep them playing orehas, Argos P1 and Orehas, Argos P1 and (rested) Chaos Dungeons and be sure to check if your gold is sufficient to outfit in the coming 1415. Find the equipment to play the 4x3 (optional +2 or +1) on dps that you are able to afford when you get close to 1415.
All in all I'm sure. I'm betting that lots of players are currently switching their top six alternates and dumping their Gunslingers. It looks good enough. 1370 alts look decent enough gold. The 1370 alts are a good place for characters to develop into Lopang alts right now too, I'd say. You can push whatever you like to be able to play further than the current limit.