LEO:
hack [coll.] - der Schmock [pej], der Schreiberling [pej]
hack lawyer - der Winkeladvokat
hack writer - der Schmock [pej], der Schreiberling [pej]

NOAD:
hack² - 1: a writer or journalist producing dull, unoriginal work: [as adj.] a hack scriptwriter.
• a person who does dull routine work.

Chambers:
hack² - ... 4: a writer who produces dull, mediocre or routine work. 5: a dogsbody. ... (adj) mediocre, banal or commonplace • hack writer.

Encarta:
hack - (adj) lacking quality and originality

Random House:
hack² - n. ... 3. a person (artist, writer) who exploits, for money, his creative ability or training in the production of dull, unimaginative, and trite work; one who produces banal and mediocre work in the hope of gaining commercial success in the arts: As a painter, he was little more than a hack. 4. a professional who renounces or surrenders individual independence, integrity, belief, etc., in return for money or other reward in the performance of a task normally thought of as involving a strong personal commitment: a political hack. 5. a writer who works on the staff of a publisher at a dull or routine task; someone who works as a literary drudge: He was one among the many hacks on Grub Street. ... —adj. 12. hired; of a hired sort: a hack writer; hack work. 13. hackneyed; trite; banal: hack writing.

Webster's 3rd unabridged:
[5]hack - (n) ... 3 a: one who hires out his professional service: one who forfeits individual freedom of action or initiative or professional integrity in exchange for wages or other assured reward: HIRELING, MERCENARY {party hacks have replaced earnest New Dealers ...}; esp: a writer who works on order from publishers b: a writer whose writings aim mainly at commercial success rather than literary quality ...
[6]hack - (adj) 1: working for hire {hack attorney} {hack critic} 2: performed by, suited to, or characteristic of a hack: MEDIOCRE, UNINSPIRED {hack writing} {the staging and lighting were mostly on a hack level ...} 3: HACKNEYED, TRITE {hack dramatic scenes}

Oxford-Duden:
hack² - 1: (n.) a: (drudge) ~~ Gelegenheitsarbeiter; Mietling (veralt. abwertend); (uninspired worker) Arbeitstier; (writer) Schreiberling (abwertend);
newspaper hack - Zeitungsschreiber;
publisher's hack - Lohnschreiber; Auftragsschreiber ...
2: (adj.) ... b: (mediocre) Nullachtfünfzehn- (ugs. abwertend)

Pons-Collins:
hack² - 1: ... b: (pej: = literary hack) Schreiberling;
the newspaper hacks - die Zeitungsschreiber;
paid hack - Lohn- /or/ Soldschreiber(in)
c: (pej inf) '(party) hack' - (Partei)heini (inf) /or/ -typ (inf) ...
2: (adj attr) (pej) (writing) stumpfsinnig

DWDS:
Stumpfsinn - 1. Haltung, Einstellung, die durch geistige und gefühlsmäßige Interesselosigkeit, Teilnahmslosigkeit, Gleichgültigkeit gekennzeichnet ist: sein S. ließ ihn stundenlang tatenlos auf einem Fleck sitzen; Manche verfielen dem Stumpfsinn; sie hörten auf, von irgend etwas Notiz zu nehmen Werner Benario 390
2. langweiliges, eintöniges, Geist und Gefühl ertötendes Tun: diese Tätigkeit ist der reinste. S.; er besorgte sich etwas zu lesen, um den S. des langen Wartens überwinden zu können
3. Unsinn, Dummheit: er redet immer wieder denselben S. zusammen
stumpfsinnig - /Adj.; entsprechend den Bedeutungen 1--3 von -sinn/; zu 1: ein s. Mensch; seine Schweigsamkeit ließ uns erst spät erkennen, wie s. er war; er konnte stundenlang s. Karten spielen; diese Tätigkeit kann einen s. machen; zu 2: eine s. Tätigkeit; zu 3: sie sangen ein s., gänzlich inhaltsloses Lied


http://dict.leo.org/forum/viewUnsolvedquery.php?idThread=722330&idForum=2&lp=ende
http://dict.leo.org/forum/viewWrongentry.php?idThread=461819&idForum=3&lp=ende
http://dict.leo.org/forum/viewUnsolvedquery.php?idThread=505336&idForum=2&lp=ende

This came up in a thread today.

I'd like to have one or two more options that addressed the shallow commercial angle, but I don't know whether you could use gewinnsüchtig or Lohn- or something in the context of, say, a painter or teacher.

Similarly, for 'party hack' a couple of people thought of Parteisoldat; I suspect that may be too positive, but I don't know if there's such a word as Parteisöldner.

Maybe others will have more suggestions from here.