There are about 100 common and uncommon creatures (including tokens made by commons/uncommons) in Gatecrash. How do you value their sizes? Consider the following charts I’ve made:
0 ||| - 3
1 ||||||||||||||||||||||||||||| - 29
2 ||||||||||||||||||||||||||||||||||| - 35
3 |||||||||||||||||| - 19
4 ||||||||| - 9
5 ||| - 3
6 || - 2
7 | - 1
1 |||||||||||||||||||||||||||| - 28
2 |||||||||||||||||||||||||||||||| - 32
3 |||||||||||||||||| - 18
4 ||||||||||||||| - 15
5 ||||| - 5
6 | - 1
Excepting rares and mythics (which don’t significantly throw off the numbers) and stat-boosting abilities (which are much harder to account for), creatures in this set are only just incrementally tougher than they are powerful, and are slightly larger than normal. What this means is, you should remember that a 2-power or 2-toughness creature is below average for this set, and a 3-toughness or 3-power creature is above average size for the set. A 3/3 is going to be pretty good this weekend, better than it was in Return to Ravnica where 3/3s weren’t big enough to profitably block centaurs, which were pretty common. How good is 4 toughness in this set? Good enough to survive a hit from all by 15 creatures out of 100.
There are a lot of creatures who can get bigger than they appear. The above graphs represent P/T as the creature is printed, for the most part. Remember that many Evolve creatures won’t participate in combat until they evolve at least once because Simic players will want to get at least some value out of their mechanic before letting their Evolvers rumble in the red zone. Also, most Gruul creatures double as pump spells, so combat math against Gruul decks can be very, very tricky. I suggest considering instead that 3/3, rather than 2.3/2.4, is closer to the practical average size of common and uncommon creatures in Gatecrash. With this in mind, a 1/4 or 2/4 (and there are a few spread accessibly to every guild) is actually a really important card for defensive decks because of how wide a portion of the creatures that will block.
Creatures with toughness 5 or better will dodge a number of very playable common removal spells, significantly more than 4-toughness creatures dodge. While 4 might be the magic number in this set for unaided creature combat, 5 is the magic number for creatures being truly resilient this weekend. Good luck.