Resistance actually takes center stage in season 2 pvp. This move was smart. It helps make it easier for people to make a choice.
Ice is very strong but I think you are misreading some things.
Fire /necro has a lot of multi hit heroes thus season. Mainly focusing on those burn heroes. Each hit of a skill will give you a stack per target. The best dpe heroes will easily stack this to 4-6 stacks. 45% attack at max. It isn't so bad. They just wanted to make the new heroes shine.
Lightning and poison are poison damage over time and electrocute which are both derivative damage. Again this is receiving a permanent 10% damage bonus which is also fine since a poison team is already strong and I expect so will electrocute.
Ice/radiance, again focused on the new heroes, ice blast, any heroes other than ice blast will not be able to make much use of this.
We already know iceblast heroes are doing great un vortex and not good in pvp.
Fire and neceo are a manage in pvp and electrocute is right there with them.
Yes, they kind of pushed older heroes to the back burner, but I am excited to see the teams people will build around this.