Targos said:
Would you allow a few artificers to cast weapon augmentation countless times on a single weapon to get a anarchic, axiomatic, disruption, flaming burst, icy burst, holy, shocking burst, unholy, wounding weapon of speed? (Thats equivalent to a +21 weapon.) Or allow somebody to cast mirror image several times getting extra images each time?
I would not allow conflicting enhancements. A weapon can not be holy and unholy. We call that "neutral" in these parts.

I likewise would not allow FLaming BUrst AND Icy Burst, or anarchic AND axiomatic. I suppose there is probably not RAW preventing it but it doesn't make much sense to allow those combinations (thought it'd be fun for a N-N PC to have holy/unholy/anarchic/axiomatic

)
Further, per DMG an item cannot exceed +10 total effective bonus. So by that rule alone I'd say the above combination is not allowable per RAW. Nothing says an Artificer can exceed this, so she can not.
Assuming I decided on a houserule that said Artificers get to exceed +10 total (non-Epic) and they had a damned good reason why holy AND unholy can go on the same weapon (for example) sure, I'd let them do it. I'd have to break the rules in yet another way as well, see below. But moving along with the thought experiment...
They'd do it once.
Then they would realize that the TEN MINUTES they spent doing it was not a good idea. Oh, you want them to use action points? Fine. They do it one time per level, as that is 10 action points. So they won't be doing it before 10th level. Technically with a feat they'd have the points at 7th level but they still won't be able to do the above sequence due to level limitation. Indeed, per RAW they can't do it at anything but high levels.
Here is the breakdown:
wounding +2
anarchic +2
axiomatic +2
holy +2
unholy +2
icy burst +2
shocking burst +2
fire burst +2
disruption +2
speed +3
Any of those require a level 4 artificer infusion. To do *all* of them requires ten. (technically since a "real" magic weapon would require +1 it's the equivalent of a +22

)
A 7th level artificer has no 4th level infusions. Assuming an int of 20, no Artificer will have 10 4th level infusions until at least hmmm Epic levels
unless he uses up higher level infusions.
So really, it isn't a matter of it being broken as the siutation you describe is not possible per RAW (+10 limit non-Epic) and if you've got any low to mid level Artificer with 10 4th level infusions, that is YOUR fault. To give you an idea of how broken the DM would be to allow that ...
If you have an Artificer w/10 4th level infusions ... that ain't a broken class. She has either sacrificed their upper level infusions (which still means a higher level artificer) or an Arti with insane INT.
How soon could it be done (ignoring other preventing rules)?
Assume an int of 20. High but in the normal-for-PC range.

You will get precisely ONE bonus infusion. This means the
EARLIEST you could get 10 4th level infusions is .... drum roll please ....
17th level.
And it would cost
every infusion slot from 4th up inclusive, as well as well over half of your action points unless you were able to wait 10 minutes, and a decent chunk of GP.
Using your APs, it would take 11 rounds before you were ready to wade into melee (must be a bludgening melee weapon). And if that isn't enough I'd bet you that the opposing party is probably not going to let you hang back and do things with your mace. Betcha that wizard in the back hits you with magic missile (at least) to disrupt your infusions (one more AP down the drain, and a lost slot. Oh dear). Maybe he fireballs your butt. Or sends a ray of exhaustion at you. Maybe he enfeebles your mind, or uses hold person, or summons a celestial dire bear or a vrock right next to you. Maybe he uses a power word on your butt or casts silence in your area (maybe an expanded heightened one even). Maybe the evil cleric is calling flame strikes down on your position.
Get the picture?
Is it now suddenly so "broken"? Ask yourself how much damage the 17th level sorceror/cleric/fighter-with-magic-weapons-like-crazy/wizard can do in 11 rounds. Ask yourself why the Artificer would not instead just whip out a scroll of Summon Monster IX and layeth down some massive smack? Why does the 17th level artificer not already have a highly magical weapon that doesn't need those infusions? After all he's had CMA&A for what, 12 levels? Any 17th level Artificer who can't make a DC 29 UMD to emulate a 9th level spell for a scroll ain't trying. In ranks and cha bonus alone, combined with taking 10 all he needs is +19. Ranks alone would do that.
Hell, twin spell MMI on a wand of Summon Monster 4 for two Celestial Lions/round, or a Maximized SM-IV for 6 small elementals per round. Get some cannon fodder out there!
Now to get it w/o 17th level. Just to see how it could be done.
Per ECSB Artificer-20 gets 4 4th level infusions/day. An Artificer with an int of 45 gets 4 bonus 4th level infusions. A total of 8. To get 6 bonus infusions would require an INT of at least 58.
ANY class with any single stat that high is arguably going to break many things. After all, any Artificer with an INt of 45 will be getting over 20 skill points per level, will have insanely high DCs (Int bonus of +17 after all). Imagine a wizard or sorcerer with an int or charisma that high. Or a Cleric with that high of a widsom.
How much would it break the game for a 10-20th level monk to have a strength (or even a con) of 58? Would you then be complaining that your fighter/monk always hits short of a 1, at does insane damage, especially on a crit?
Picture a fighter with a +23 to strength and damage. He's got a keen rapier, and improved critical. Every threat is a crit. He thus crits on what 12-20? So almost half the time he'll be doing double damage for what 2d8+48? Potentially doing that several times per round, and at no cost.
Granted, that's the extreme case and using higher level slots can help but not that much since you start out with less 4th level slots (first one at 8th) but now we've established the extremes.
Even for combat giving up your 5th and 6th level infusions is not necessarily a good trade. After all, 6th level infusion allows you to put vorpal, dancing, or brilliant energy on instead.

Not to mention disable construct (for those pesky enemy warforged), repair critical (for those pesky friendly warforged), Wall of Iron (Can topple onto foes

), and disrupting weapon (far better than adding disruption).
Come on everyone, read the whole ruleset that applies. There
IS a limit, several in fact, to how many weapon enhancements an artificer can put on a weapon. First and foremost their infusion limit. Additionally the +10 limit. And let us not forget, action points are a precious commodity (especially at higher levels) as is time: taking 10 minutes or 10 rounds is a heavy price to pay in a combat.
Even if you have an Arti with 10 4th level infusions available, his action point limit will keep him from doing this more than one time per level. And he still won't be doing it before 17th level without the DM's help. Not to mention the question "why the heck would he bother with this at 17th level?".
No houserule to "fix" it needed, but a houserule or two are needed to make the "broken" behaviour happen.