Looking at this deck, I would make several changes.
Pithing Needle is much more of a SB card than a maindeck card. I would cut it from the main and probably only put 2 copies in the board.
Young Pyromancer should be a 4-of if you have them, and
Sigiled Starfish should be cut, as the random scry effect does not come online fast enough to allow you to fully utilize it. If you have
Serum Visions, I would add those in place of the Needles you are cutting.
Dispel and
Spell Pierce are also counter magic options you can consider as well. I'm also not a huge fan of 1-shot dudes, like
Hellspark Elemental. While it works in a
pure burn deck sometimes, it's not that strong in a deck like thi. I think I would consider cutting all 4 of them to allow you to run more spells in the main (counters probably) to further enable Delver flips and Pyromancer making dudes.
You have A LOT of lands that enter the battlefield tapped. Trying to make a 3-color deck in Modern happen without fetch lands or
shock lands is really tricky. I would consider the M10/Innistrad lands as a better option to the temples, as they at least have the possibility of
entering in untapped if you control the proper basic land type (Sulfer Falls,
Glacial Fortress,
Clifftop Retreat). Additionally, the new Battle for Zendikar lands meet the requirement to help these come into play untapped (
Prairie Stream is the relevant one, and helps each of the 3 previously mentioned lands enter untapped)...in fact, if you went 4 each of each of these 4 lands (16 total), plus 4 islands, 2
plains, and 1 mountian, you would have nearly perfect mana, and about 1/8-1/4 the cost of the typical Jeaskai mana base. this would also free up another slot in the deck to add another spell, or raise your Angel or Rider count by one.
Cancel and
Dissolve should not be in the board. if you want more counters in the baord, I would add whichever of the previous ones mentiond did not make the cut (
Dispel/
Spell Pierce). You can probably shave one of the Veridcts and one of the Shatterstorms to also open a couple slots. If we assume you cut those 8 spells, and add in 2 Needles, and 4 possible additional counters, you still have 2 slots for something like
Shattering Spree,
Vandalblast,
Stony Silence, Wear/
Tear, etc.