I believe that if Taiko maps are included with a song, they should follow similar difficulty spread rules that osu! uses. This basically means there should be an easy/normal Taiko map if there is an Oni map. Too many new players lose interest in taiko because they can't play the hard difficulties (labeled Oni, something most newbies don't translate to "insane"). The Taiko maps made from normal beatmaps suffer from too many rolls, simple patterns, and no training value.

So yea. I'm half asleep and allergic to air, so ignore anything that seems too ridiculous about this

At least these days limitation of number of difficulties increases to 8, I don't think lots of owners of mapsets, which are mostly osu standard mappers, are eager to give more than 1 empty slots to Taiko guest mappers. This suggestion is reasonable but we cannot force it.

But maybe we can mention this as recommendation or guideline, though not in the rules.

The thing is...
1. Most osu Easy/Normal could be converted to taiko fine. (though not perfect), so there's no really need to do so.
2. Though we have 8 diffs max, some mappers (including me) still wants a 6 osu standard mapset, that means, won't have enough slot in some of the cases.
3. Assuming we now have a 6 osu +2 taiko set, the 2 taiko should probably be Oni + Inner Oni / Muzukashii + Oni because these diffs makes the most difference with osu converted map, should be solved first.

So yeah, agree with lepi, guideline is fine, rule is no.

@^: About #1, personally I don't think that is fine enough to be 'fine', but whatever. Agree with your opinions.

With number one... not really. Rolls in taiko are usually used 4-10 times in a song, instead of 20-40 times. Most converted songs are either fully don (red) notes, mostly sliderrolls, or just so boring for new players that they don't learn anything from the map and they actually get deterred from continuing playing Taiko.

2. This would probably increase the number of allowed maps if they are Taiko or CtB maps your trying to fit in.

3. Almost the entire suggestion is making it so you can't have oni+ inner oni without having an easier difficulty (not muzukashii, lower). Normal osu maps being played on taiko do not provide a valid supplement for an authentic kataan or futuu difficulty, because of reasons I posted above.

If I remember, it was been discussed that non-standard mapsets had to follow similiar mapset rules to standard mapsets.

You can't enforce this on "standard mapset", but you can on "non-standard" Taiko-only ( or Taiko+CtB-only ) mapsets.

e.g. a map with 4 Taiko, should have at least one easier difficulty.

Thing is, authentic/full taiko mapsets are pretty difficult to find. Searching "Taiko no Tatsujin", "Taiko Authentic", or even the song name usually doesn't get you results (yes I made sure I was searching all beatmaps, not just ranked). It's really difficulty to start playing taiko because authentic mapsets with the easier difficulties are hard to find for newbies, and standard map sets only have Onis and Inner Onis. This suggestion would put taiko maps in a similar state as osu! standard maps when it comes to difficulty curve. If you have a Taiko Oni, you should have a Taiko Kataan/Fuutuu. You don't have to make 4 different taiko diffs, just have an easier one.

Taiko and CtB mapsets have been permitted recently, what you expected? In the past someone did create some "Authentic" Taiko maps by mapping them while respecting the Taiko original pattern... you remembere the "Taikosu" or so, right?

Hm, I agree with your points Mithost.
But what NatsumeRin said is also not that wrong.
lepidopodus is also right with the said things.

But about futsuu... well that's such a problem.
Personaly I would like to see more futsuu, but it's hard to have Futsuu + Oni because of the diff spread. Muzukashii + Oni fit's here better and as lepidopodus said many times before: Oni represents the style of a mapper really good. - so we can't force them to map Futsuu or Muzukashii.

At least adding this as guideline would be not a bad idea.

Also @ Mithost, please change the name of the topic to ,,[Taiko | Guideline] Taiko maps Difficulty spread" so Sakura sees that this has something to do with the taiko rules/guidelines.

I think he means Futsuu + Muzukashii + Oni

I'm just generally saying there should be an easier difficulty taiko chart when there is an Oni/Inner Oni. An easy Muzukashii or something would probably suffice.

Basically something like how I started doung in my maps (this) (adding a Muzukashii)

Well, you can't avoid people doing 2+1 spreads and not accepting guests, though

The reason i extended the difficulty limit was in hopes of seeing better taiko spreads, just saying.

This. (Sorry if I make promotion for it. orz)
Threads like the Easy Taiko Map Project made me thinks about this.
So I added to my new Map, which will be submitted soon, a Taiko Diff (a Futsuu) because they're too less easy Taiko Diffs out.
I made it myself; it isn't so hard like I thought, even if it's just a Futsuu Diff. ^^

Well, tbh it worked allready a bit. At least I noticed it. Got more chances to map 3 diff's at once, as you said Muzukashii+Oni+Inner.
http://osu.ppy.sh/s/45107 - http://osu.ppy.sh/s/41885
Anyway, back to topic. As I said, if people and you agree, we may add this guideline into the taiko guidelines.