For some reason, the "ORB" Effect in dota was a very simple system to understand. If the ability or item said "ORB EFFECT" In the tooltip, they did not stack. In some versions of DOTA some of these were broken, but in HoN lets get down to the Combat Effect Modifiers. The tooltips for these are confusing as all hell.
You have "Morph" Items, which says that they apply a combat modifier. However items like the Cranium Basher (+ Stun) was not an ORB Item in DOTA.
Then you have lifesteal items, which other than the Vladimirs Offering (Abyssal Skul) were also considered ORB Effects, but in this game they are considered Exclusive modifiers. They state that they cant stack with other lifesteal items, however Abyssal Skull and Lifesteal do stack.
Then you have characters like MageBane, Slither, etc. Who have abilities that possess "ORB" Effects in dota, such as manasteal, or slow, or poison. Another example would be Arachna in this game and its web slow. This is similar to the ice arrows Drow had in DOTA. If you used ice arrows, your other ORB Effects would not stack. So now you have a character that can get an extra ability that dota would not allow on each attack, since they are not prevented in this game.
Magebane can use Lifesteal + Stun + Mana leach (passive combat)
Arachna can use Lifesteal + Slow (Web) + say chain lightning.
Please word the tooltips better! Make some obvious thing saying this is an ORB Effect, and it doesnt stack with other ORB effects. Period. Dont make it so compliated in the tooltips.
Also, since you allow stacking of these abilities in this game, some heroes are more powerful than their dota counterparts, or allow item combinations that dota does not, thus unbalancing them from the years of balancing dota has gone through.
There is nothing like 'orb effects' in HoN. There are 'General' and 'Attack Modifiers'. The stacking system is different from DotA. You can read more about it here.
Btw, the 'orb effect' in DotA was everything but easy to understand. There were 'orb effects' that didn't stack and then there were 'buff placers' that didn't stack either, but for some reason there were also some 'buff placers' that actually did stack with 'orb effects' and other exceptions which made the whole system unintuitive and confusing.
Also, terms like 'orb effect' are completely made up and meaningless about how they actually stacked or not, because all the DotA orb effects and buff placers are based on about 6 different attack-modifying skills provided by the WC3 engine that have shown a completly differently atacking-behaviour among one another.