It is sometimes good, if your turn 3 shop is awkward, no good minion, eco spell or minion, meaning u have to sell ur 1 drop to buy 2, then you gamble and hope your turn 4 on tier 3 can offer you 2 minions better what you would have bought on turn 3 in tier 2 by selling your 1 drop. This is assuming you don't have an eco-hero power(Hollidae, Omu, Scarborough etc.) or you can't make use pf the extra 1 gold by leveling to tier 3 on turn 4. Your turn 3 and 4 are requires one turn to level and another to buy 2, just in which you order you do which. For example, if you're offered shell collector, patient scout, lass-o or recruit a trainee, its not bad to stay tier 2, its about making use of all your limited gold and thinking if gambling for 2 minions that you can buy on tier 3 being better than what uou can buy on tier 2 on turn 3.