  We investigate unification prospects of two heavy scalar triplet extension of
the standard model where, in the absence of any right-handed neutrino(RHN),
type-II seesaw accounts for current oscillation data with hierarchical neutrino
masses consistent with cosmological bounds and the lighter triplet decay
explains baryon asymmetry of the Universe via leptogenesis. We note that the
absence of RHNs in the fundamental fermion representations of SU(5) delineates
its outstanding position compared to SO(10) (or $E_6$). In addition SU(5) needs
smaller scalar representations ${15}_{H1}\oplus {15}_{H2}$ compared to much
larger representations ${126}_{H1}\oplus {126}_{H2} \subset $ SO(10) (or
${351}^{\prime}_{H1}\oplus {351}^{\prime}_{H2} \subset E_6$). We show how
precision gauge coupling unification is achieved through SU(5) with the
predictions of different sets of two heavy triplet masses which, besides being
compatible with type-II seesaw, are also consistent with unflavoured or $\tau
-$ flavoured leptogenesis predictions for baryon asymmetry of the Universe. In
addition to an intermediate mass color octet fermion, completion of precision
gauge coupling unification is found to require essentially the presence of the
well known triplet fermion dark matter (DM) near TeV mass scale. The model
capabilities to accommodate observed relic density, direct detection mass
bounds and vacuum stability of the standard scalar potental are also pointed
out in the added presence of a scalar singlet DM whose mass could be as low as
$\sim 62$ GeV. With GUT scale $\simeq 10^{15.54}$ GeV, proton lifetime
estimations for $p\to e^+\pi^0$ are presented as a function of an unknown
parameter.
