Hunter's Mark really bothers me. When I first read and tried it out I thought it was great but I quickly realised:
(1) It's incredibly resource heavy for what it does,
(2) renders dual wielding almost completely pointless for one of only 2 classes that get offhand damage bonus,
(3) scales incredibly badly versus, for example, Thief Sneak Attack that does more damage more reliably with no Concentration requirement or Bonus Action use.
Honestly I'd like to see casting it be a lvl2 class mechanic like Action Surge rather than a spell, which recharges on Short Rest; and reapplying be a Free Action. But that will probably get me in trouble with the 5e RAW crowd...