This could potentially be pretty oppressive. Each trigger helps the next trigger fire off. The first proc will be a wild guess, but the information gained from that first one can be used for the next creature spell. Yes, the opponent gets ETB triggers and a replacement spell, but you just need to name correctly name something that's useless. On the other hand, there's some counterplay for the opponent - play all the weak spells first so that only strong spells remain, giving you a Sophie's Choice. (Like the Tribute mechanic.) Watch this card carefully.
See Hypnotic Specter and other Specters for an idea of how overpowered that ability is on a 3-drop. Also landwalking and shroud are dead, and hexproof (replacement for shroud) may be dead in the next year or two as well.
There's a much cleaner template you can use here. See also Ride Down.
Haste, trample
Whenever ~ becomes blocked, flip a coin. If you win the flip, tap each creature blocking it and remove that creature from combat.
4/4 would still be plenty strong for a 3-drop. See also Loxodon Smiter.
Maybe try +1/+1 and lowering to 3cmc if playtests show they're not that exciting.
They're not perfect mirrors here. One effectively draws you that card, while the other is not a discard. A closer mirror would be for both to put your topdeck into your hand and then gain/lose life, or for both to mill the top card and gain/lose life from that. For cards clearly meant to be mirrors, you definitely want to make them better mirrors.
Not sure that template can actually work. Try one of these.
Destroy up to two target artifacts. For each artifact destroyed this way, you may put a time counter on a creature.
>Yes, this one uses a doubled template ala Seeds of Strength.
Destroy target artifact. If you do, you may put a time counter on target creature.
Destroy target artifact. If you do, you may put a time counter on target creature.