i wonder if i can beat the game without a wizard. my druid has some offensive spells which might help.
i am at neverwinter now, and am a fighter/cleric, have a pure fighter (Ironfist), a tiefling rogue (Neeshka) and a druid (Elanee).
Will my path onwards be very difficult or should I have a wizard from now on?

I don't have a wizard, and I'm pretty far into act II. If anything, the game is probably a little too easy, most of the time. It seems easily doable without a wizard.

yes.
the part i will miss is that i love the fireworks.

Having lots of AoE spells comes in handy at certain points, but I would think you'd be OK with just the druid. She has a few reasonable ones and can always summon if crowd control is needed. Only thing is that she doesn't have that many spell slots and you'll probably want her to have plenty of buffs memorized for awkward fights. Still, certainly doable from what I've seen of the game.

yep
playing icewind dale series needed a wizard.
but a druid that can summon companion, creatures, and has buff and offensive spells will certainly do.

Having only a druid is quite doable. To counter the lack of spell slots, give him\her any wisdom boosting items you come across to get the wisdom bonus maxed.

Druids in particular are nice because they have a number of longlasting buffs for the melee crew - barkskin, stoneskin, resist elements spells, tortoise hide, allowing your meleeers to do the heavy lifting while sustaining minimal injury.

My current play-through is mage-less. I'm playing a cleric (who can cast fireballs and ice storms!) and have been sticking with melee-ers and the rogue. Doing just fine.

If you have the use magical item skill, you can probably do without a wizard or druid, but an item is not realy a replacement for a spellcaster.

And honestly, Neeshka's use magic device skill is maxed, and it is pretty rarely that I even bother to use it. There are very few what I would call "tough" fights in this game, even the bosses going down disapointingly quickly. Typically arrow, steel, and a few invocations from my warlock are more than enough to win a fight. I have Elanee use all of her long duration buffs, and only bother having her cast offensive spells in the rare instance that my party needs a little extra assistance.