I think we can all agree that the master engineer hero has some really unimpressive abilities, the dwarfs' main strength (according to TT at least) is artillery, one would really think that the engineer to top them all would really be more interesting than one bland ability not to mention its passive ability is somewhat useless, i mean +6% explosion??? its a useless passive for most ranged units of the dwarfs who do not deal explosive damage. Now im not here to discuss balance saying that he is currently UP im just saying that he is bland. I would suggest a similar approach to that of the black coach meaning that he could have three abilities and using one would put them all in cool down. These abilities would improve range or accuracy or damage. This way you could really leverage the master engineer and make him a really interesting choice because you could use him to specify what you want off your artillery and ranged units.