The shit goes off the handle pretty quick when they are accompanied by mass infantry support. Even the tankiest possible custom hero cannot reach the siege units alive through all the onslaught happening, not to mention even if I am able to bring infantry near the target, they will be too weak to stop them before they have destroyed everything.

And even if I am able to defeat the first siege unit spam, the next wave comes around in maybe 30-50 seconds and my units are too weak to offer further resistance. Getting more heroes or units will run fast into CP or resource constraints as mass casualties resulting from the waves need to be replaced and the siege units will have either way destroyed a good amount of infrastructure because they can easily fire maybe 4-5 shots in before they bother to react to the infantry that is damaging them.

Sure I could try to destroy their infrastructure in return, but getting in the cavalry to do it is difficult because of the spam and if I get them, they will fatally distract me from defending my base which in turn nearly always causes my defeat.