I'd like to amplify what Raven said - teamwork and skilled play in the dungeon is worth a lot more than +2 to hit, AC, and saves.
Let's take a look at the "3 token 10 packs" claim for hardcore and see how it shapes up for dungeons of HC difficulty matching that of 2016/17 based on the modules.
Median non-boss monster AC: 21
Median boss AC: 24
Median non-boss monster HP: 210
Median boss HP: 290
With 3 token 10 packs, a party would have access to 30 packs. This would give the whole party an expectation of, with 2018 tokens:
3-4 +1 weapons.
3-4 +1/2/3 STR items (2018 was unusually generous in this regard).
So let's just say everyone in the party gets +1 to hit over whatever is on the party card.
Let's assume we bring a Bard and they do Bardsong, and a Cleric who casts Bless in room 1, and Prayer in rooms 2 and 3.
This gives the party bonuses of:
+3 in combat rooms 1
+4 in combat room 2 and the boss room
For such an undergeared party, the best makeup will be I believe to drop the Paladin and Rogue (for low geared groups the auto-damage of the Wizards is very strong).
This gives a net to-hit bonus of:
monster/boss
Barbarian: +6/7
Bard: Will be doing bardsong
Cleric: +2/3 (casting spells first round)
Druid: Will be casting spells
Dwarf Fighter: +6/7
Elf Wizard: Will be casting spells
Fighter: +7/8
Monk: +5/6
Ranger: +4/5
And meaning the slide classes need to slide to hit:
Barbarian: 15/17
Cleric: 19/20
Dwarf Fighter: 15/17
Fighter: 14/16
Monk: 16/18
Ranger: 17/19
Given those to-hit numbers I'd guess the party hits around:
2 slides per round vs. monsters
1 slide per round vs. bosses
At these gearing levels the party is going to be getting about 10 damage per slide hit. Assuming 4 rounds per room the party will deal around: 80 damage to regular monsters and 40 to bosses.
Over the course of the dungeon the party can count on ~220 damage from the spellcasters.
This is just not enough damage to kill monsters at Hardcore (even assuming the whole party survives to keep dealing damage).
That being said, for an optimized red build - the kind of thing you can put together for ~$50-100, your party would be sliding at ~+10 to hit, hitting on ~1/2 their slides, and dealing ~100 per round.
So, I believe HC is doable with an optimized red build, and strong teamwork (e.g. ensuring you have the right classes, ensuring your Bard is always on, ensuring your Cleric is Bless/Prayer/Prayer in round 1 of each room, making sure you go fast enough to always get 3/4 rounds of combat in).
An example such build would be:
Melee class:
Defender Set - +13 AC, +1 saves
Boots of Agility, +2 DEX
Necklace of Natural Armor, +2 AC
Belt of the Berserker, +3 STR, -2 AC
+1 two handed weapon, +1 to hit
Lenses of Heimdall Sight, +1 to hit
Shirt of Brawn, +1 STR, -1 DEX
Wicked Charm, +1 STR, -1 saves
Gauntlets of Ogre Power, +2 STR
+2 damage bracers, +2 melee damage
+3 and +2 damage with two-handers rings, +5 damage
+1 damage with two-handers charm, +1 damage
Ioun Stone Beryl Prism, +1 to saves
+2 Cloak of Resistance, +2 saves
Ioun Stone Faceted Amber, -2 from ranged and spells
Ioun Stone Ruby Rhombus, -3 from fire
Pants of Springing, -1 from melee
Charm of the Salamander, -1 from fire
Which sums up to:
+6 to-hit, +12 to damage
+14 AC
+3 to saves
Reasonable damage mitigation (5 from fire, 2 from ranged and spells, 1 from melee).
Add in maybe a Charm of Health and an Earcuff of Vitality for a bit more HP.
