asm
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Well, 1-2-3 is definitely too much... the expert skill should have an effect similar to a major skill, in this case, similar to the potion.
Let's say 0-1-2 or 1-2-2 would be quite enough, in my opinion.
It also makes sense to remove the bonus in case the tent is destroyed.
And add more hit points to it - for example, 75 (without skill) - 150 - 225 - 300 (expert).
You could keep the old effect, but change the ranges:
1-20 / 20-50 / 50-75 / 75-100
I don't see the point in removing the health bonuses; health shouldn't depend on the presence of the tent.