As a solo, I'd add a few things: First, some kind of ability when it is bloodied, perhaps a boost to its attacks...Maybe while bloodied, he gains an action point when he misses with both attacks using Dwarven Might?
Second, increase the recharge to at least 5, but I think 4 is probably better.
Third, the normal +5 to all saves is missing, and I'd throw in some protection from stuns, as well.
Fourth, Dwarven Battlecry needs a duration on the attack bonus.
As is, Thuldin's offensive abilities are rather limited, and he'll probably end up attacking twice with his axe most rounds, with his immediate reaction ability triggering only once or twice. In addition, he has nothing to help him against ranged bombardment. Perhaps something like:
Thuldin has a +2(maybe more?) to all defenses against ranged and area attacks from 5 or more squares away.
Take a look at this
for comparison. It's a older solo, so it has more HP, and supposedly less offensive power. However, it has one more attack each round for more damage, an aura that disrupts PC plans, a rather powerful immediate reaction power that will trigger pretty much every round, burrow, resist, and a better blast power.
Removing the limitation on Won't Be Intimidated, or changing it to something else, would make it far more useful and likely to trigger. Shifting is also a major component of battlefield movement, and since solos often degenerate into standing slugfests, removing that option is even worse.
Idea: Keep the restriction, but Earthshaker, at recharge 4 or 5, pushes as well as creates difficult terrain. Then, have Dwarven Battlecry recharge when Won't Be Intimidated is used.