Working on a RBW Reckoner for Standard. Opinions/Advice welcomed!

A few thoughts:

First, why not include some more board-based damage spells?  You have Blasphemous Act, but not much beyond that.  I can see where Rolling Temblor or Magmaquake could prove quite useful - as they both can deal with hexproof threats like Invisible Stalker and Geist of Saint Traft while hitting your Reckoners and Dolls AND triggering your Blood Artists.

Second, there are a few cards in here that don't really look like they belong.  For instance, Dark Impostor is in here to do what?   Why only one of Searing Spear and Murder?  Both spells are good, but only one of each?  You have Boros Charm in as a 2x, but what're you using it for?  You're not likely going to use the double-strike option, other burn spells like Searing Spear might do less damage, but are far more versatile (and easier to cast), and you really won't need to make anything indestructible (the doll already is and you want your stuff to die to trigger Blood Artist).  Entreat and Lingering Souls?  I get that tokens are there to help you trigger Blasphemous Act, but why not aim high for something like Assemble the Legion which would help you set off the act and then replace all those tokens the very next turn.  Why Lili?  I'm not seeing where she's really helping much.

Third, Inquisitor's Flail is hilarious with Reckoner/Doll type effects.

Lastly, why only one Stuffy Doll?  At that count you're unlikely to pull it.

Anyway I hope some of this helps.  Good luck.

From the way you describe each of the various cards, many of them sound like items that should be in the sideboard, not mainboard.

How do you deal with Predator Ooze/High Priest of Penance?  Simple, Tragic Slip.  Mind you, it can  deal with Falkenrath Aristocrat too.

There's a definite trade-off between Magmaquake and Murder.  On the one hand, Magmaquake will let you damage your guys, wipe out plenty of creatures in one move and hit a bunch of triggers at once; but, on the other, it's a sorcery AND could end up hurting you by taking out your blockers (nevermind the weakness to flyers).  Murder, conversely, gives you instant speed removal for their Thundermaw Hellkite/Resto Angel/etc.  So what's the solution?  I say to run two of each - there's seldom a case when you're going to complain that you have too much removal.

Esper Tokens - if this is a problem at your LGS/local meta, they printed Illness in the Ranks in Gatecrash which single-handedly destroys all spirit tokens (at least until they play Intangible Virtue) and would similarly shut Sorin, Lord of Innistrad down completely.  Put 2-3 in your sideboard if it's a matchup you envision seeing frequently.  Similarly, if you prefer more of a spot solution, Electrickery overloaded will deal with all those tokens.

Ultimately you're going to be more familiar with your local meta than I could be and playtesting will provide the best answers to what is and is not working.  But again, most of the oddball pieces strike me as being things for the SB.