I had thought about Rowskin's idea before and the only reason why I didn't suggest it is that players might purposely cede flag control to draw out priests... But the more I think about it the less likely that scenario seems. Leaving the HP flag, CD flags, gold mines, etc. in enemy hands probably wouldn't be worth forcing the priest spawn.
- Sedna is screwed because no AoE means less ability to tag creeps
I think this is more indicative of a general issue with Sedna. Either a yeti improvement or an AoE damage effect tagget onto her heal at every level, starting at maybe 50 damage would help a lot with the tagging.
- Everyone will gain XP/Gold faster, making late game characters come into their own faster.
This is an issue they may need to address sooner or later though, many games have. WoW, had issues with spell scaling, so did Diablo II and Warcraft 3. I hate to just list Blizzard games, but they're the first ones that come to mind. I think some artifacts that increased ability damage by x% or y amount would be an interesting experiment, but I wasn't in beta so I don't know if that had already been experimented with (first problem I can see is a lack of anti-scaling factor like armor).
For the most part I don't really even have an issue with late game scaling, just late, late game when people get their 4x crits and 8-10k HP. Before that point I feel most DGs are still competitive so I'm not sure the hastened game timeline would be an issue.