I’ve been on an absolute tear recently. I am something like 16-4 in my last 20 matches of M15 limited.
I think this is for multiple reasons including very good luck, but I would also like to relate it to how I have been evaluating creatures with 1 point of toughness. In each color there is a premier two drop with 1 toughness: Red has [card]Altac Bloodseeker[/card], White has [card]Oreskos Swiftclaw[/card], Blue has [card]Welkin Tern[/card], Green has [card]Satyr Wayfinder[/card], Black has [card]Child of Night[/card], and even the artifacts have [card]Bronze Sable[/card].
The two best colors in the format have premier answers to all of these threats. Red has [card]Forge Devil[/card] and White has [card]Raise the Alarm[/card]. To a lesser extent black also has answers in [card]Black Cat[/card] and [card]Crippling Blight[/card] but they are not cards that even consistently make your main deck.
This format requires that you play between 4 and 6 two drops in all of your decks. This forces people into playing with all of these very vulnerable creatures. Yes, one or two of these in your deck is good and can even be great, but you must be cognizant of getting blown out.
In many situations you cannot simply attack your two drop into two open mana if any of it is white. Playing with restrictions is never good and so in many situations I simply prefer to either draft another creature or spell over a 1 toughness two drop, or draft a different two drop instead. Red and White have the best examples of this in which I draft both [card]Kinsbaile Skirmisher[/card] and [card]Borderland Marauder[/card] very highly.
However you choose to use this information, I just implore you to reconsider how you draft and build the lower end of your curve.