Hirsch I wrote:1- Unlimited sources of haste are problematic, to say the least. it is a very powerful effect, both for escaping or destroying
your enemies, and it does not matter which build you are playing, it is normally worth the investment. the spell was nerfed several times, and did not stopped being a must for almost every character that can possibly cast it.
I don't think Haste is too powerful. Being able to get in more actions essentially just lets you win in some battles where before you only had a narrow margin of victory. Any good spell can make you suddenly feel more powerful after you learn it and start to use it--for example, Sticky Flame or Fireball. The player is strong in Crawl, but Crawl still offers plenty of challenges.
When you "normally worth the investment"... I think that might be your own bias (for example, if you play a lot of spellcasters with nice aptitudes). I think you should come up with statistics that support such a claim (or define it better in the first place). sardonica's citation of the 0.13 tourney is a statistic that counters your statement.
2- it does not provide a decision, for most builds. you will want to get the spell sooner or later, the only choice is when to do it. also, it reduces the number of options for any character: the XP used to train charms will not be used creatively, to adapt the character to the situations it found.
Putting experience into a skill is a fine decision. Say, if you play a centaur hunter, you might think of that as getting bows skill + fast 2 mutation (potentially a similar effect to Haste) in exchange for lower spell-related aptitudes (similar to having put experience into spellcasting and charms). But you don't say "It's a given I want to choose a centaur hunter for my combo". You might as well complain that playing a DEFE is a nobrainer because of course you'll aim for Fireball Fire Storm etc.
3- potions of speed and wands of hasting are adequate substitutes, and limited, so hasting yourself before every tough fight is not an option.
4-it can stay as a monster spell, so the changes that need to be done are minimal.
(These aren't reasons to make the change, they are just minor comments on why such-and-such wouldn't cause a problem if the player Haste spell were removed.)
Maybe it's true that every or nearly every spellcasting-oriented species has decent enough combined spellcasting+charms aptitudes that if you're training spellcasting anyway, the strategic benefit of Haste is worth the investment at a certain point in the game (in most cases). So? That's far from every species, and far from every type of game that people may play within that species. And as I alluded to before, even if you know you will want to learn it, knowing when to devote experience to something is always a huge strategic challenge, given how every combo is different and every game within that combo is different. And Haste does have strategic value. Just like the basic act of moving around tactically to control line of sight in Crawl is something
every player can utilize, Haste increases the amount of actions you can take but what actions you take are up to you (and are the chief factor in determining whether you live or die).
When articulating a proposed change, people are often prompted to answer "What does this fix?", but rather than simply trying to say what about the spell needs fixed, I think it's worthwhile to describe a specific experience of yours where Crawl (as it is now) let you down. I have invested in Haste many times before, but I have never felt "Wow, it was so obvious to start to train for Haste now" or "Wow, now that I've learned Haste Crawl is easy". Maybe I'm just not enough of a Crawl master to make the most of Haste... I think that Haste is a well-designed spell because learning it lets me deal with a broader variety of threats, but far from every threat.
"Maturity: among other things, the unclouded happiness of the child at play, who takes it for granted that he is at one with his play-mates."
- Dag Hammarskjöld