You're oversimplifying German grammar.
In antiquity strong verbs used to follow 7 regular schemes, now they diffused in over 180 subgroups, with many groups only consisting of only one verb.
So if you say those are mostly regular then English verbs are regular too, since they are the cognates of those strong verbs and in most cases you can apply the same "rules":
German: Ich singe, ich sang, ich habe gesungen English: I sing, I sang, I have sung
After trying to learn some languages I can tell you that non had a regular verb system. Just try to cope with Russian (or Slavic) aspects.
And in English you don't have to bother with many suffixes for different persons, 3rd person singular has an s, that's it.
Most English speakers don't even know what a subjunctive form is ("If I were you!"), while you have to learn and apply 4 subjunctive forms in Spanish.
OTOH you're right that English is very heterogeneous, mostly because Norman French was for centuries the language of the upper class, which resulted into an amalgamated creole language with a totally confusing orthography.
German profits from the fact that over centuries many scholars - and most prominently Martin Luther - tried to translate foreign (mainly Latin, Greek and French) constructs into corresponding German constructs to make them understandable for simple people, especially the language in the mass!
Dia/rrhea Greek "flowing through" Durch/fall German "falling through" grand-père French "Big Father" Groß/vater German "Big Father" flood light English Flut/licht German
So many German terms are more easily understandable by analyzing the parts.
And standardization of German - especially of orthography and pronunciation - happened for political and historical reasons very late in the 1880s and was always driven by compromising between the dialects in different autonomous regions to find a common base for a highly decentralized culture sphere.
Standard English OTOH was dictated by the slang of the cliques from Oxford and Cambridge and reflects a pronunciation as it was centuries ago in London's centralized realm. (with exception of the differing English of Scottish parliament)
So yes English has problems, but certainly not the verb system. =)