in terms of time investment
We'll continue making adjustments as necessary to keep 10- and 25-player raids within a relative alignment, in terms of time investment, difficulty and rewards. It may never be perfect, but we still see interest in both raid sizes for different reasons. And ultimately we'll continue designing 25-player raids as long as there are a decent number of guilds wow or interested in the format. We've seen no evidence as of yet that such interest is waning to any degree that should cause us great concern.
We tend to begin raid design around 25 players anyway before tuning for the various sizes and difficulties. That, when combined with our intent to carry on with 25-player Raid Finder group sizes, makes it very much worth our time to continue designing 25-player raids.
Regardless of what players' personal preferences or opinions are regarding the varied raid formats in World of Warcraft, we don't see removing options as a smart choice in the foreseeable future.