They do require severe stat investments to make them useful, either as a full caster (with a backup weapon) or a hybrid (which would mean you are less powerful than either a dedicated sorcerer or a dedicated warrior). It can be done, don't get me wrong (got a pure caster and a pyro meself as well), but you'll end up with rather squishy chars. I believe that, if you're not yet familiar with enemies and surroundings, the best tactic is to use a 100%, high stability (great)shield, and just keep moving with your guard up to prevent ambushes getting you. Works rather decent actually (of course, you shouldn't always have your guard up, but it helps prevent damage against sudden enemies appearing).
I do agree though that casters (and sorcerers most so) trivialise PvE; Equip boost damage boosting rings and the slumbering dragon ring, 60 int, court sorcerers staff, scholar's candlestick, use hidden body, and just sneak past everything. Only spell you really need is Great heavy soul arrow, and maybe Crystal souls spear (although I prefer GHSA, since it's the most dmg/fp efficient)
And indeed, a 40/40 int/fth pyro with all the damage+ gear + chaos bed vestiges (or great chaos fire orb against very slow targets/ seething chaos against immobile targets) will nuke everything as well. In fact, I've got a hypermode-invader planned using only CBV