a couple of things
unless you're on lone wolf, your skills will be spread quite thin if you attempt to max out 3 different schools on the same character. you can give an aero/hydro character a level or two in pyro and/or geo for haste/peace of mind/fortify if you feel the need, but putting equal points in aero/hydro/geo or pyro will probably just harm your overall damage output. this is just my experience, it's possible your damage will still be fine if you get tons of int, but also keep in mind that doing 3 schools means memorizing even more spells, so you'll need to pump lots into memory as a result. in short, i wouldn't recommend doing this if you are not on lone wolf
with regards to the death knight, if he's currently on sword and shield then the damage output will be quite low early on (i don't know where you currently are in the game). bouncing shield will become okay once you equip a decent shield, but the rest of the damage output won't pick up until maybe mid to late act 2, coming completely online in act 3 (bouncing shield will be one of the highest damage skills in the game by this point). overall, a sword and shield character will likely never do as much damage as a two handed character, but the extra armor and stats a shield gives you is quite useful, becoming quite significant later on (though it's significant as early as fort joy on tactician when everyone's scrambling to get as much armor as possible). so it's a trade off that depends mostly on what other kinds of damage you have available to you. it's by no means a bad option though
