Tornado spamming can be VERY annoying for DK, but it can be gotten around and punished, you have several options.
If you have a full shield ,keep that **** up.
If your shield is depleted dont keep it up but try to roll out(works, just try it).
If your shield is small take it like a man and get hit, afterwards dont try to airdodge back down, because you will get caught in it again. Float to an edge,where you will be safe from the tornado.
Remember there are two types of tornado, the rising tornado(the MK player hits b many times), this one is invincible, so dont try to beat it if you get hit by it, airdodge through the sides since he has to rise up.
If he stays grounded your giant punch will beat it or an ftilt will clash it out, and if you get sucked in and he decides to stay grounded and to catch your airdodge on your way down give him the old DK dair spike which will def. go through.
Ive gotten pretty experienced at this matchup lately, IMO its a slight advantage for MK, like 55-45 MK.Nothing too serious since you can kill him at 70, haha,