I respectfully disagree, especially when considering I top out at 4 mana for only 2 cards (Jace/Sorin, Verdict in the board.) I was playing Jeskai Delver for over a year with only 18 lands, with basically the same curve, and I almost never faced mana issues. Yes the cantrips are weaker than Legacy but when it comes to finding lands and smoothing out draws, Serum Visions is at least as good as Preordain. Opt isn't as great, but I am also getting the land count up to 20. Testing will find out if I'm wrong, but this is another reason for avoiding Cryptic. That 5-6 mana is to flashback Cryptic with Snapcaster. The most I'd ever need is 5 mana to flash back an Esper Charm with Snapcaster, and I'd rather hedge against flooding than hedge against mana screw. Twenty seems to be fine to me.
*shrug* Maybe you're right and testing will reveal that I need more lands. I would cap out at 22 probably, but if I did that it would be another Ghost Quarter and a fetchland.
EDIT: When I'm drawing cards off Esper Charm and Remand the lands tend to find their way into my hand as well. If I get too pinched on 20 lands I'll squeeze in another Opt + Land, or two lands.
Dark Confidant is an idea I have toyed with, but I don't know if that's the direction I want to take. I'd probably do something disruptive like
Tidehollow Sculler before I did Confidant. Confidant is just a different deck, and playing 6 drops like Tasigur is risky. Yes cantrips, but I can't always avoid it.