This brought me to think that for the warlock:
Not enough spells to cast. Spamming EB is fun at first but it gets boring fast. Doing the Hexblade is fun, but most prefer to either play an EK (for a magical martial character) or simply go for a full fledge martial character with no pact and with feats. For my players, it seems that the warlock is a caster that does not know what he really wants to do. The versatility of the warlock depends a lot on what he is willing to sacrifice to get it. Don't get me wrong, the warlock is strong. But mechanically something simply does not add up. Maybe a few more spells or a bit more pact features... I simply do not know. Most of the players that play a warlock (from their own admit) are doing it for a change of flavor and only if there is a wizard in the group...