On first glance, we might think these are asking “too much.” On the other hand, these are cards which are rarely sent (aside from the Advanced Arsenal). When cards are rarely sent it is because the opportunity cost is too high. Put another way, other cards are just better and there’s not enough justification to give those up to get one of these. If we start with the base assumption that we should be giving players a meaningful choice between cards they’d actually want to use, these (aside from the Arsenal card) need a buff.
The explorer cards in general are pretty poor. The only times I really consider them is if I’m going to be actively using them alongside my main army. Sioux and Iroquois chiefs both offer buff auras. The Indian monks offer a debuff aura. Aztec, Inca, and Chinese chiefs are great front-line tanks and powerful fighters in their own right. And the African civs can stack up 3-4 explorers with cards. For these, it makes total sense to get them a 50% hp bonus so they can do their jobs longer.
But for the other explorers, a generic 50% hp buff, minor attack bonus, and niche on-use ability everyone forgets to use just don’t cut it. Giving Spain more war dogs would fit well with their early game focus, helping them pull off a stronger Age 2 archaic unit rush with the dogs being strong enough to snare. +3 dogs would probably be balanced (8 total), but +5 (10 total) would be worth a play test to see if it’s too strong.
I’d be interested to see other Euro civ explorers get buffs.
Tavern cards are cards which really aren’t worth sending unless you’re planning a revolution that relies on outlaw units like Barbary States. Otherwise, there’s no reason to use it. Getting a tavern wagon and +1 to the limit (for extra exp trickle) might be enough to make it worth using.
I would not buff the Advanced Arsenal card. The bonuses it offers are more than worth the card on its own. No need for a wagon.
The trade post cards are tricky. Honestly, I’d like to see trade posts get their own natural attack at baseline for trolls who send 1 unit to peck at the things for 10 minutes. Getting a discount on the trade post doesn’t seem terribly appealing since it would take a ferocious fight over the things to ever build enough to make the resource cost justify the card. Offering a buff to the resources granted at each interval would be too strong on maps with large numbers of post sockets.
Perhaps the solution to make an advanced trade post card worth it is: 50% hp buff, tower-like auto attack to defend itself, trade posts build in half the time without an active builder (100f, 100w pathway to build them)?