You imply that Dain´s ability is the same but he does not give +1 defense and his ability "only" works when he is ready.
The argument that there are not that many silvan heroes right now isn´t really valid seeing as more heroes will be added at some point.
It'll be rare to get enough readying abilities on the board in round 1 to actually make use of more than 1 stat point per hero, and I really don't think giving each hero +1 of a stat for a single round would be game-breaking at all. A readying ability can potentially be.more powerful than that and can often last many rounds.
Dain's ability is a good comparison, even if it has obvious differences. It only has a 2 point stat boost, but it can potentially apply to a LOT of Dwarves and lasts from the beginning of the game until Dain dies. It has the restriction that Dain needs to be ready, but a simple readying effect can remedy that for the most part and he can always just be saved for attacking, so everyone can still get the willpower boost.
The proposed first-turn boost to three stats on Silvan heroes seems much weaker to me by comparison. We're talking about a boost that is limited to 1 turn: the turn where the players are typically the weakest, and in numerous cases, where the encounter deck can be at its strongest.
The argument about the number of Silvan heroes that are available is pointless because it does not take into account the future of the game. In any case, this post is simply an idea that likely won't be implemented, at least not on Celeborn. It's not worth the amount of arguing we are doing about it.