What do you mean by competitively?
As in the style one plays when fighting human opponents. AKA the meta game. Unlike AI, human players will go for the kill as soon as possible (not always a rush, but they'll be able hit you where you're most vulnerable in a way the AI could never do), so only the most effective strategies can really be used in this situation. Thus competitively, using envoys to get pacts only makes sense when you have two "eco" players (in large team games, its possible for players to start surrounded by only friendly players, so these players have no direct threats to worry about and work on building their economies to support players on the front lines) who will both benefit the most from the pacts and won't be fighting early on anyways.