For group there is :
T1 - which is non-prestige (same stats as HH Sebilis heritage gear), i.e 4400HME values 10% better than Tier 2 EoK
T1.5 - this is Tradeskill gear, non-prestige as well, 4750 HME values
T2 - Prestige - 5100 HME values
Rough calculation - I'm averaging the HME values, so some slots might have 5300 HME (i.e Breastplate), but some slots have like 4700 for the same tier.
Its about a 21k HME value bump from EoK Tier 1 to RoS Tier 2 (subtract about 250 HME per slot for the lesser tiers), if you account for all 21 slot gear, which the way mobs hit, isn't going to make any bit of difference 95% of the time whether you wear EoK Tier 1 or RoS Tier 2. A 25k-30k quad combat round isn't going to make any difference from EoK Tier 1 vs RoS Tier 2.
So if your purpose is to buy the expansion for just solely for the gear upgrade for your f2p toon, you are shit out of luck for the most part. This isn't accounting for 10% spell power or AA power bump, but then they always bump mob power by 20-25% to compensate!
Also all augments are Prestige, including Tier 1 augments. So you are out of luck on that as well.