Maybe defensive pacts need to have their length shortened (25 turns on standard time)? I personally don't experience issues with them (recently), but I can understand the problems others have; ultimately I think the dp's are actually just doing they're job by agitating other players (humans included), and dissuading them from using physical force. I think it's just the nature of the feature, and maybe others might be inclined to just play with dp's disabled if that were an option. Maybe set a limit so that a player may only have 1 active dp at a time? It's not really ideal, but people might enjoy that kind of thing.
My only gripe has always been that there's no way to see how many turns remain in dp's between AI (although I understand the reasoning behind this as well). It's just an annoyance for me.
The only way around this I’ve found is to repeatedly have a unit target an “enemy” each turn to see if the DP is still active.
Don’t sanctions end trade deals? I’ve noticed that if you sanction a Civ in a DP the alliance stays active, so maybe we can remove that protection? It’s unlikely that a warmonger is going to have enough votes to brute force sanctions through the WC, but if they do get it passed I think this would be a nice option against DP’s.