I’ll try to summarise my tl’dr post on reddit regarding the cards you brought up and why they aren’t as good as some people might think. Of course these are just my opinion but I think that goes without saying.
Xho like other battle pets don’t contest mana tiles early on which can be very powerful for songhai with lantern fox, IF (or no IF if you have a PF already), vortex into Phoenix Fire on their 2/3 opener for huge tempo. Later turns it’s just too slow to die to be useful with the potential to get a situational spell like defiler or ghost lightning.
Katara in short is decent but suffers in the same way other backstab minions do in that they rely on other useful cards to get in and do work for not a great payout only to then die due to their low stats in the best case scenario and worst case, they put their backs against a wall.
Shadow waltz is bad because it doesn’t make gore horn work with mirror meld while screwing it out of IF range, requires a lot of backstab minions to be in your hand to get value out of it when songhai also needs a mix of spells in their opening hand especially movement spells in the case of backstab cards otherwise you’re just paying for blank minions while other factions aren’t as you won’t ever get a backstab off.
Ki beholder seems good but not in any archetype that currently exists as the minion slots are incredibly tight right now if anything I could only see them in backstab lists so kaleos’ blink could get you a backstab without mds or jux.
Coil is just a meme if you ask me, because Xho is just meh, Ace is one of the biggest jokes in a line full of bad battle pets and nothing else in songhai seems to promote a strong battle pet deck that other factions wouldn’t do better.
Crescent Spear is ok but the +1 doesn’t offer much more for phoenix fire at 4 and makes twin strike margianlly better at taking out weenies and you’re right about it not being currently good along with storm sister and eight gates.
Pandamonium is just too slow. It’s worse than meta imo because you need to pandamonium, crescent spear, ghost lightning which is up to or the same mana if played in 1 turn and costs you 3 specific cards that you needed to keep in your hand for this situation instead of 1, can’t punch it to clear like meta and it transforms your own minions too when a lot of songhai minions want to retain their buffs.
Battle Pando is also just ok because without DSS it really isn’t doing too much pinging enemies for 1 once or twice and with it, it needs to either survive a turn / not get dispelled or you IF it which costs you yet again 3 specific cards and 5 mana which you will then run the pando into his face and nothing else for that turn (since it will clear the minions with DSS) only for it to die to a normal general attack on their turn and place another huge threat on the board and you have quite an empty hand. Oh and it’s also susceptible to Zen’Rui.
Onyx Jag is ok and might have potential which I mentioned in my previous post.
In summary most of these cards aren’t good enough to do anything for current archetypes and backstabhai while getting support didn’t get anything good enough to make it better than arcanyst or spellhai let alone a top tier deck.
Relasine’s stream starts in 4 hours from now I believe and I’ve never watched it but he will be hosting it along with UnoPro, WickedFlux, etc who are obviously prominent songhai main players that will give their opinion on the cards so I would recommend tuning in if you’re interested in what they think.
Apologies that it is lengthy but it was the shortest way I could write it while giving good enough reasons